diff --git a/data/uking_functions.csv b/data/uking_functions.csv
index f4354395..b4afdd46 100644
--- a/data/uking_functions.csv
+++ b/data/uking_functions.csv
@@ -93732,8 +93732,8 @@ Address,Quality,Size,Name
 0x000000710122b2b8,O,000152,_ZNK4ksys4phys6detail13ModelSkeleton9Allocator16getAllocatedSizeEPKvi
 0x000000710122b350,O,000296,_ZN4ksys4phys6detail13ModelSkeletonD1Ev
 0x000000710122b478,O,000036,_ZN4ksys4phys6detail13ModelSkeletonD0Ev
-0x000000710122b49c,U,000812,
-0x000000710122b7c8,U,001048,
+0x000000710122b49c,O,000812,_ZN4ksys4phys6detail13ModelSkeleton18constructFromModelERKN4gsys7ModelNWEPN4sead4HeapE
+0x000000710122b7c8,O,001048,_ZN4ksys4phys6detail13ModelSkeleton18constructFromModelEPNS0_17ModelBoneAccessor15ModelBoneFilterERKN4gsys7ModelNWEPN4sead4HeapE
 0x000000710122bbe0,O,000088,_ZN4ksys4phys17ModelBoneAccessorC1Ev
 0x000000710122bc38,O,000148,_ZN4ksys4phys17ModelBoneAccessorD1Ev
 0x000000710122bccc,O,000156,_ZN4ksys4phys17ModelBoneAccessorD0Ev
diff --git a/lib/hkStubs/Havok/Common/Base/Types/hkBaseTypes.h b/lib/hkStubs/Havok/Common/Base/Types/hkBaseTypes.h
index 2067471d..1321f5e8 100644
--- a/lib/hkStubs/Havok/Common/Base/Types/hkBaseTypes.h
+++ b/lib/hkStubs/Havok/Common/Base/Types/hkBaseTypes.h
@@ -198,7 +198,7 @@ struct hkResult {
     HK_FORCE_INLINE bool operator==(hkResultEnum e) const { return m_enum == e; }
     HK_FORCE_INLINE bool operator!=(hkResultEnum e) const { return m_enum != e; }
 
-    HK_FORCE_INLINE bool isSuccess() const { return m_enum ^ HK_FAILURE; }
+    HK_FORCE_INLINE bool isSuccess() const { return m_enum == HK_SUCCESS; }
 
     hkResultEnum m_enum;
 };
diff --git a/lib/sead b/lib/sead
index 06a028cb..88f9a684 160000
--- a/lib/sead
+++ b/lib/sead
@@ -1 +1 @@
-Subproject commit 06a028cbf382e5b997d17d3a8147dbdbb7f66109
+Subproject commit 88f9a6841aadf1740accb1f7def1bc5d6f347d2b
diff --git a/src/KingSystem/Physics/Rig/physModelBoneAccessor.cpp b/src/KingSystem/Physics/Rig/physModelBoneAccessor.cpp
index 52be352a..5165f5ee 100644
--- a/src/KingSystem/Physics/Rig/physModelBoneAccessor.cpp
+++ b/src/KingSystem/Physics/Rig/physModelBoneAccessor.cpp
@@ -4,7 +4,12 @@
 #include <gsys/gsysModel.h>
 #include <gsys/gsysModelNW.h>
 #include <heap/seadExpHeap.h>
+#include <heap/seadHeapMgr.h>
+#include <nn/g3d/ResSkeleton.h>
+#include <nn/g3d/SkeletonObj.h>
+#include <type_traits>
 #include "KingSystem/Utils/SafeDelete.h"
+#include "KingSystem/Utils/Types.h"
 
 namespace ksys::phys {
 
@@ -28,8 +33,11 @@ public:
     bool constructFromModel(ModelBoneAccessor::ModelBoneFilter* bone_filter,
                             const gsys::ModelNW& model_unit, sead::Heap* heap);
 
+    /// Construct a Havok skeleton from a gsys model. Fast path, no support for filtering.
+    bool constructFromModel(const gsys::ModelNW& model_unit, sead::Heap* heap);
+
     hkaSkeleton* mHavokSkeleton = nullptr;
-    u8* _10 = nullptr;
+    u8* mSkeletonStorage = nullptr;
     void* _18;
     Allocator mHavokAllocator;
 };
@@ -55,8 +63,99 @@ ModelSkeleton::~ModelSkeleton() {
         mHavokSkeleton = nullptr;
     }
 
-    if (_10)
-        util::safeDeleteArray(_10);
+    if (mSkeletonStorage)
+        util::safeDeleteArray(mSkeletonStorage);
+}
+
+bool ModelSkeleton::constructFromModel(const gsys::ModelNW& model_unit, sead::Heap* heap) {
+    mHavokAllocator.mHeap = heap ? heap : sead::HeapMgr::instance()->getCurrentHeap();
+
+    const nn::g3d::ResSkeleton* skel = model_unit.getSkeletonObj()->GetRes();
+    const int num_bones = model_unit.getBoneNum();
+
+    if (num_bones <= 1)
+        return false;
+
+    mSkeletonStorage = new (heap, 0x10) u8[sizeof(hkaSkeleton)];
+    mHavokSkeleton = new (mSkeletonStorage) hkaSkeleton;
+
+    if (!mHavokSkeleton->m_bones._reserveExactly(mHavokAllocator, num_bones).isSuccess())
+        return false;
+
+    if (!mHavokSkeleton->m_parentIndices._reserveExactly(mHavokAllocator, num_bones).isSuccess())
+        return false;
+
+    if (!mHavokSkeleton->m_referencePose._reserveExactly(mHavokAllocator, num_bones).isSuccess())
+        return false;
+
+    mHavokSkeleton->m_bones._setSize(mHavokAllocator, num_bones);
+    mHavokSkeleton->m_parentIndices._setSize(mHavokAllocator, num_bones);
+    mHavokSkeleton->m_referencePose._setSize(mHavokAllocator, num_bones);
+
+    for (int i = 0; i < num_bones; ++i) {
+        const auto& bone = *skel->GetBone(i);
+        mHavokSkeleton->m_bones[i].m_name.setPointerAligned(bone.GetName());
+        mHavokSkeleton->m_parentIndices[i] = s16(bone.GetParentIndex());
+        if (i == mHavokSkeleton->m_parentIndices[i])
+            mHavokSkeleton->m_parentIndices[i] = -1;
+    }
+
+    return true;
+}
+
+bool ModelSkeleton::constructFromModel(ModelBoneAccessor::ModelBoneFilter* bone_filter,
+                                       const gsys::ModelNW& model_unit, sead::Heap* heap) {
+    if (bone_filter == nullptr)
+        return constructFromModel(model_unit, heap);
+
+    mHavokAllocator.mHeap = heap ? heap : sead::HeapMgr::instance()->getCurrentHeap();
+
+    const nn::g3d::ResSkeleton* skel = model_unit.getSkeletonObj()->GetRes();
+
+    ModelBoneAccessor::ModelBoneFilter::BoneBitSet bones_to_keep;
+    const int num_bones = bone_filter->filter(&bones_to_keep, model_unit);
+
+    if (num_bones <= 1)
+        return false;
+
+    mSkeletonStorage = new (heap, 0x10) u8[sizeof(hkaSkeleton)];
+    mHavokSkeleton = new (mSkeletonStorage) hkaSkeleton;
+
+    if (!mHavokSkeleton->m_bones._reserveExactly(mHavokAllocator, num_bones).isSuccess())
+        return false;
+
+    if (!mHavokSkeleton->m_parentIndices._reserveExactly(mHavokAllocator, num_bones).isSuccess())
+        return false;
+
+    if (!mHavokSkeleton->m_referencePose._reserveExactly(mHavokAllocator, num_bones).isSuccess())
+        return false;
+
+    mHavokSkeleton->m_bones._setSize(mHavokAllocator, num_bones);
+    mHavokSkeleton->m_parentIndices._setSize(mHavokAllocator, num_bones);
+    mHavokSkeleton->m_referencePose._setSize(mHavokAllocator, num_bones);
+
+    const int num_model_bones = model_unit.getBoneNum();
+    int havok_bone_index = 0;
+
+    for (int i = 0; i < num_model_bones; ++i) {
+        if (bones_to_keep.isOffBit(i))
+            continue;
+
+        const auto& bone = *skel->GetBone(i);
+        mHavokSkeleton->m_bones[havok_bone_index].m_name.setPointerAligned(bone.GetName());
+
+        int orig_parent_index = bone.GetParentIndex();
+        if (orig_parent_index < num_model_bones) {
+            mHavokSkeleton->m_parentIndices[havok_bone_index] =
+                s16(bones_to_keep.countRightOnBit(orig_parent_index) - 1);
+        } else {
+            mHavokSkeleton->m_parentIndices[havok_bone_index] = -1;
+        }
+
+        ++havok_bone_index;
+    }
+
+    return true;
 }
 
 }  // namespace detail
diff --git a/src/KingSystem/Physics/Rig/physModelBoneAccessor.h b/src/KingSystem/Physics/Rig/physModelBoneAccessor.h
index 7cefd835..1480bf3d 100644
--- a/src/KingSystem/Physics/Rig/physModelBoneAccessor.h
+++ b/src/KingSystem/Physics/Rig/physModelBoneAccessor.h
@@ -3,8 +3,8 @@
 #include <container/seadBuffer.h>
 #include <gsys/gsysModelAccessKey.h>
 #include <math/seadVector.h>
+#include <prim/seadLongBitFlag.h>
 #include "KingSystem/Physics/Rig/physBoneAccessor.h"
-#include "KingSystem/Utils/BitSet.h"
 
 namespace gsys {
 class Model;
@@ -21,8 +21,10 @@ class ModelBoneAccessor : public BoneAccessor {
 public:
     class ModelBoneFilter {
     public:
-        virtual void filter(util::BitSet<1024>* bones_to_keep,
-                            const gsys::ModelUnit& model_unit) = 0;
+        using BoneBitSet = sead::LongBitFlag<1024>;
+
+        /// Returns the number of bones after filtering.
+        virtual int filter(BoneBitSet* bones_to_keep, const gsys::ModelUnit& model_unit) = 0;
     };
 
     ModelBoneAccessor();