'95 GSX, break shudder, rear rotors

1995 GSX

My car began shuddering under moderate breaking about 10,000 miles ago (@ 100k now). At first I ignored it, then I changed the front rotors, which seemed to help a little. My car still shudders, but only under moderate breaking, if I break hard, or lightly, I've got no problems.

(I think I scare the other drivers by approaching stoplights too quickly just so I can break hard lol)

So, a mechanic buddy of mine suggested that if it shuddres and the steering wheel doesn't vibrate, it's probably the rear rotors. So I bought two rear rotors and am in the process of trying to replace them. The problem I'm having is that I can't get the darn things off. I moved the caliper and the two bolts that hold the bracket in place, but it doesn't budge. Am I missing something? I'm afraid to take a hammer to it until I'm sure I'm not missing a bolt. The rotor around the studs is pretty rusty, so I sprayed some wd40 on it hoping it would break loose... no luck. Suggestions?

Thanks all.