I only let the mattress hang over about an inch on the front so that your calves weren't against the platform trim. You don't have to do the overhang, was just my preference to do it that way. I used 1/2" on my project, I did do a 1/2" sub frame which was glued and stapled to to the bottom of the ply, but really was to build up to give the hinge some surface to screw to.
pics on this post: http://familywoodworking.org/forums/...189#post411189
To a small child, the perfect granddad is unafraid of big dogs and fierce storms but absolutely terrified of the word “boo.” – Robert Brault