IIRC, wasn't there something in one of these 4.1.x updates that mentioned something about being able to handle multiple ins -> one channel? Something about vocoders?
sorry, kinda lame response but if you search the forums or the version history, you should be able to find it.
also, there's a freeware compressor out there, that I believe is both PC / Mac compatible, that does sidechaining via Left / Right input iirc. again, I don't have the specifics

Lame I know. Japanese, that may help (or not), it might have been SlimSlowSlider or something like that
