NeilBlanchard -- Excellent. Consider making a foam block that is a negative impression of the convex edges as a sanding block to maintain the edge contour along its length.
justme1969 -- I am interested in that material. Any brand name, or what should I ask about at the local sign shop? I'd want to chemically strip the paint if it's not available without.
EDIT: Here is a manufacturer:
http://nudo.com/. Available locally for $104.95 for a 1/4" sheet.