The character could still move, just the lower legs / feet clipped into the ground. The HipHeight calculation is discussed in the below post.
https://devforum.roblox.com/t/humanoidrootpart-positioning-adjustment-for-automatically-scaled-humanoids/258555
I didn’t replace the RootPart so I was thinking maybe the Player’s original RootPart position was causing the HipHeight to be off. That doesn’t appear to be the case because the HIpHeight is the same value regardless of the clipping issue.
Maybe I’m running into the " Changing the assets on a character while also using the HumanoidDescription system could lead to undefined behavior" warning described in the HumanoidDescription System article and that is causing the clipping.
humanoiddescription-system
I’d like to use the HumanoidDescription (HD) to do the morph if possible. I saved off the parts associated with the LeftArm (LeftHand, LowerLeftArm, UpperLeftArm) and attempted to set that using a HD. It updated the size of the arm, but the Mesh didn’t get applied. I’m using a Mesh a friend uploaded and now I think I might be running into an issue described in:
https://devforum.roblox.com/t/humanoiddescriptions-is-there-anyway-to-use-custom-assets-not-owned-by-you/239721
I was able to use Player:ClearCharacterAppearance to remove most of the accessories. It says that doen’t apply to t-shirt or face so I can just manually clear those out.
Thanks for the ideas!