I put one on my big ski, a 96 GTI, it made a big difference with handling, couldn't tell about top end, probably about the same.
That being said, the 96XP has way different handling charactics anyway (jump on and hang on), I can't imagine it would make much difference, could make it more unstable. But hey for 5 mins. work try it, let me know how it works.
Yes... if it's a top loader... you will feel a night and day difference in the hook-up in choppy conditions, AND, you will feel more planted in corners. BUT... expect to loose 2 mph up top in smooth water.