Along with my hand obsession, I also have a molding and casting fetish.  If something looks like it would work as a mold....I use it.  I took one of those disgustingly cheapo plastic RIP tombstone that I got at the party store and molded one of plaster.  I had to reinforce the bottom of the tombstone form with a piece of wood to prevent sagging and when I poured the plaster, I used duct tape from side to side and from top to bottom.  I made several plaster tombstones and excluding the first one, they turned out pretty good.  We will be making plaster cherubs for a tombstone accessories so make sure you also get in on the tombstone making.  I will have several other 'molds' available if you are not into cherubs.