Would it help if you made your trap line a touch longer so you are lower?
Have you tried placing your feet further together or further apart?
When you crew, do you handle mainsheet?
The geometry of where the crew is (vs where you are as skipper) is of course, different, especially when handling the main.
Do you think you are 'working too hard' and therefore tensing up?
Let us know how it goes.
1989 Hobie SX18 Sail # 1947 "In Theory..."
'Only two things are infinite, the universe, and human stupidity. But I'm not sure about the former.'