Sounds like your on the right track then. I'm not doing clips on the walls either but, my walls are not touching the joists except every 4 ft with the other style of clips to isolate the 4 walls of the room from the ceiling. Depending on the size of your room shouldn't be very high dollar. Might be well worth it. The walls would just be an inch short of the joists and then the clips. Maybe one of the other guys can chime in on the gasket, I haven't started my window plug yet. I know i'm using a couple of layers of mdf and gg for the mass and damping in my window well but, haven't looked into a specific gasket material yet. So much to do!