Creates six invisible box collider parts welded to R15 limbs to approximate classic R6 collision geometry. The engine spawns six invisible Part instances (head, torso, left arm, right arm, left leg, right leg) parented to the character and welded to the corresponding R15 body parts. All original R15 mesh parts have their BasePart.CanCollide, BasePart.CanTouch, and BasePart.CanQuery disabled and are made massless; only the HumanoidRootPart retains mass so it remains the physics assembly root.

Overrides each R15 mesh part's collision physics with inner-box geometry derived from the standard R15 scaling model. The engine recalculates every MeshPart in the character with collision data from the default R15 model's bounding dimensions, producing tighter collision volumes that follow the avatar's proportions without adding extra parts. This is the default value of LegacyCollisionMode.