contearchitect

Thank you all for your responses. It is indeed a lampshade I was going for. The pyramid solution suggested by Alaskan Son is perfect. I built a solid of the correct size and shape and then subtracted a slightly smaller one to hollow it out. 

I've spent way too long trying to find a way to modify a cylinder or pedestal shape. It seems only the base and height are adjustable, and the top radius is just along for the ride. How do I get the dimensions I want for this shape?  I looked at the article on bell-shaped footings, which is a little complicated and not exactly what I want.

Thanks.

I broke the wall where it becomes an interior wall and defined that portion as you advised. It worked! Thank you! 
 

Very new user here x12.  When I cut through an existing masonry wall how do I finish the end of it? The baseboard returns, but the drywall does not, so I see the wall in section. Thanks.

Scheme D - Copy 3D.pdf