Jim, I think the hull design is the limitation on the PA, not the fins. Putting the same fins in both boats you already noted the difference in response. Even doubling the power output of the Drive would not add that much zip to the PA -- I was able to try this effectively with the Outback and rudder mount evolve motor combined with Turbos, where doubling the power added less than 1/2 MPH to the top speed.
Note that the charted PA evolve performance against evolve Outback (below) shows the same pattern. Neither the PA or the Outback can perform like the Revo, but in all cases there are diminishing returns with added power.
Incidentally, the existing Tubofins have a lot more thrust potential than most users can muster. Most users get tired after running the Revo 4 or 5 miles at 5 MPH, yet those same fins can easily push the boat to about 7 MPH (requiring about 3 or 4X more power). If you've got the legs the Drive can provide the thrust.
This may sound like a strange thing to say, but if a person is not replacing parts on the Drive very often they're not pushing those fins to their full capabilities. Fortunately, very few people can -- the newest Drives can usually go 800 to well over 1000 miles without a part replacement for most people, barring a defective part.