I have a buildt-in bookcase with a 1/2" ply back that [nearly] meets
up with a wall that is slanted in at the top at 45 degrees. The back
of the case and the wall are painted with the same flat wall paint. I
want to put a cove at the junction of the plywood and drywall,
probably with a 2-3" radius. That means that the material I build the
cove out of will be up to 3/8" thick. I have both plaster of paris and
drywall joint compound. Which should I use and why?

PS: A molding strip is out--I want to camouflage this intersection,
not highlight it.

PPS: I guess that Lew is going to suggest epoxy with microbubbles. How
hard would that be versus plaster or mud, and what would be the
advantages?
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