I need to use the slab roller rather than a rolling pin in order to get even thickness. Yes, I know you can get even thickness with a rolling pin. However, there's a really nice slab roller in the clay studio and I see no need to reinvent the wheel.
Using the clay bodies I'm using, I need to keep the slab at least 3/8" thick. If I want a thin cover, I will have to consider using a clay that's either all porcelain or at least 1/2 porcelain.
Jim did some glaze experiments with ^10 and I love some of the colors he got. I may switch to a ^10 body. I'd prefer not to use B-Mix - my experience has been that B-Mix slumps rather badly. I do have some B-Mix reclaim and I may do one or two test covers to see if I will have the slumping problem.
I'm also thinking I need to make a depression around the holes in order to accommodate the screw head. I want to see how these work before making any firm decisions.