---

I think your in the range. The factors you posted above are what is holding your top speed down a a little. I rarely drive at top speed anyways and couple mph difference doesn't feel that much faster.

A little more on the 15' speeds from my observation. There is a speed (which is probably prop dependent on lift) where the boat lifts out of the water. Thinking back to when my boat had a 60Hp Evinrude and Jack Plate {jackplate is worth 2-3mph} The best top speed was 45mph in the right conditions. If the hull would lift I could hit 44/45 mph. If the conditions were not right, I ran 42/43mph. The downside to the hull lifting out the water, is chine walking shortly follows.