I have an 05 21 stealth/ultra with a stock vortec 6000 (350hp). I put the PD droop and ride plate on and tested it out a couple of weeks ago at Lake Elsinore.
Before my average speed was around 50-51 mph. Now with the new set up, I ran 53.5 mph (GPS at 4500 rpm). I did my research on the droop and ride plate. For my budget and the set up of my boat (no shoe or ride plate), the PD worked best. I also ran the droop with out the ride plate. My speed dropped and it took longer to plain.
I know the PD may not work on some boats, but it worked for mine.
Just my 2 cents-Anthony
There you go probablecause about 3mph with very little work. On yours it my be a bit more.