what's good to use to adhere the muffleing foam to the head. we've been using this stuff called liquid nails, it seems to hold up ok, but it comes undone on bass 5 often due to more vibrations

I usually use contact cement and cement the foam to the shell of the BD with about 1/8" to 1/4" of foam extending beyond the bearing edge of the BD. This does two things. First you will get better adhesion to the porous wood surface than to the head, and that overhang allows for even muffling around the head.