I have an 2003 22 Daytona with 496HO. The boat runs a constant 80mph and I have seen 82mph on a couple of times with a labbed 28 bravo. The boat has a High X dimention and is very hard to plane. I added Dana fixed tabs last year to cure a porpoise problem and it worked but did not help the slow speed. I was told there is a fin that you add to the bottom of the drive similar to the ones on a fishing boat to help planing and low speed porpoise.
Have you tried these and do you sell them?
I am going to add a whipple and would like to cure the problem before I have props done again.