box can make a world of differance with sound, although if you put alot of liquid nail, it should hold... and i dont know about liquid nail not holding for a long time, i havent used it on mdf but i know my dad use it to put backsplashes on coutnertops, so plywood-drywall and pulling that off on stuff over 20 years old, usually the wall or plywood pulls out before you seperate the liquid nail.