I own a 1998 Yamaha GP800 with few hours on it. I enjoy the machine other than the porpoising issue I'm sure you are all aware of. After some research I have concluded that the following is the best fix: Riva Trim Tab Kit P/N# RY2717. Unfortunately Riva has discontinued this product so I have to find someone with a set kicking around. The kit retailed for $59.95 new. Please reply if you have a set you want to get rid of and I will get your contact info.