In which conditions?
In the flat, my 550M/L will swerve side-to-side if my toes tap on the pedals. It's one of the habits I'm still trying to get rid of. Push hard with the heel but keep the toes steady. I can tell how bad I am doing by pulling my feet way off the pedals (which hurts after a short period) and watching how the boat goes completely straight. Ooops!
Upwind with overhead waves slightly from the side the boat gets thrown around quite a bit and a lot of rudder corrections are necessary, at least that's my experience. I have the feeling the longer boats fare better, but it's hard to tell.
