theres really no need to add foam, just get some dum dum (a tar like substance, kinda sticky, somes in strips, the guy at the store will know what it is...) and stick it between where the top piece and the bottom piece meet all the way around, then put it togeher, tap it, and put some between the top and bottom where it still rattles by the screws.
This kept everything pretty light, and nice and quiet.
Oh, and watch those aluminum screws, make sure the screwdriver fits them near perfectly, because the buggers like to strip.