Add 3' of stone to existing vertical siding

[Dennis Charb]

I do have Pro. I have a completed plan that I wanted to add the rock to the lower portion of the wall. When I change it to a pony wall a line at the correct height shows up, but the siding remains. If I delete a wall and redraw it as a pony wall it does work. I tried changing to a pony wall in 3D with no results.

If I create a test plan with standard walls and then change to a pony wall it works correctly.