Rudder adjustment - have weather on the starboard tack.

I have a Hobie 17 Sport....I think it is the last year that they were made; I have sailed this one for 6 summers. This year, though, in addition to the centerboard issues when dragging it up on the sand, we have a heavy weather helm on the starboard tack, WE have seemed to try everything; i.e., switching he rudders, moving the main back on notch, adjusted and re-adjusted the rake , the toe in, etc. Although it has gotten better over the summer, it still is a heavy weather helm on the starboard tack - especially in 20+ winds. Does any one have any suggestions that we have not tired....probably there's a real simple fix, that my boat partner and I don't know of. Thanks.