I used some comet and some tilex and some oxyclean and some other stuff on my first Hobie 16 tramp. I sold it a year later, so I have no idea what long-term damage this might have caused. Although there were no immediate affects (other than a sparkling clean tramp), my gut is telling me that using those chemicals didn't help in the long run.
You're best bet will be to visit a local marine store for some advice. I'm quite sure there's a middle of the road product that won't degrade the fibers of the tramp.
Hope that helps.
Mike