I gained 5 MPH but probably would have gained more. I also changed the ratio from 1.5 to 1.36. The engine I have in the boat now doesn't have enough torque to push the boat properly with the lower ratio. I am building a new 598 cube NA engine this winter.
The boat handles better with the shorter drive and will fly with neutral trim where I had to trim up last year to get it to fly. I am happy with the changes. I should have my new prop from BBlades this week. I had to modify the trim rams and drive for more negative trim so the boat would get on plane with the 4 blade BRAVO prop. I am running a Bravo 28 that came off of the SCARAB right now. I absolutely love the thrill of a cat. The feel of the boat when it is flying and going in a straight line and it just loosens up and takes off. gives me goose bumps.

In the last few weeks I installed a cable type trim indicator and an air/fuel ratio meter.
I am in the process of dialing in the HP950 carb.
Best money I ever spent was the O2 gauge.
Oh - and I installed the Bimini for those sunny hot days. ( not many of those this summer here )