I'd say there are more effective damping materials than felt - but perhaps harder to work with.
I'll check: pressed mineral wool, cotton pads, pressed kapok. No fibreglass unfortunately.
About attaching - the best thing you can do is lacquer it with an acoustically transparent lacquer without damaging the porous surface. Most elastic lacquers work for this purpose.
Edited by AstralStorm - 1/22/14 at 12:32am