I have a Cort Yorkville Semi-hollow body and experience the same problem. The post about the EQ may work because I defenitly noticed my guitar's body has a resonant frequency around 440 A. With the right amount of distortion, I can hold an A all day, go for a bite and come back and it's still "AAAaaaa". Sorry I can't add much info though because i've yet to try stuffing it, I just use my strat, but i've been told it works. Thanks for posting though, I'd forgot I had this problem. Enjoyed the advice.
-Scott
