Add 3' of stone to existing vertical siding

[Kbird]

I found with existing walls I changed to pony wall ,that if I changed the wall type in plan view the wall didn't show the pony wall in a 3D view but if I change the wall to Pony Wall in the
3D view itself it does show the pony wall as expected , you can also set the height for the split in wall types.

The OP must have AHD or Pro as he has the Pony Wall option apparently.

M.