Today I recieved the two 15" passive radiators for my subwoofer. Now I can get started with rabbeting out the holes in the enclosure to be the correct size, and finally paint the enclosure. The passive radiators have a textured black finish on them, and build quality appears to be superb, with an extra thick cardboard tube between the 3/4" thick diaphragm and the spider, and the cast basket.I have a question: When I drill holes for and set the T-nuts, should I just drill the hole big enough to accept the whole center shaft of the T-nut and then glue it in place or should I first drill a hole the size of the machine screw and then drill the bigger hole to accomodate the T-nut's shaft? Also, I have some solid oak trim pieces that I made from an oak board. Should I sand them before I stain them and apply the polyurethane?