Just throwing this out there. Our 1989 Hobie 18 has, over the last few times out (& with no consciously made adjustments), been pulling to weather on port tack and wanting to turn downwind on starboard tack. Does this sound like it's more likely due to rudder adjustment than mast rake?

Yeah - sounds like rudder rake issues. One rudder is too far out (weather helm) and the other too far under the boat (lee helm).

Make sure your rudders are properly locking in the full down position. I believe the newer castings have a set screw that allows fine adjustment.

Check Hobie's website and forum. Lots of good info about how to set rudder rake.

Thanks. (I just saw this). THe problem seems to have disappeared, but there had been an issue with the starboard ruddeer not locking down fully. That might have been it,