Good to hear and fully agree ref your #1 point. They are better looking and do provide you with a place to mount things.
My boat was 4LHA powered. And we cruised at 15kts at 2800rpms. According to the manual, you are dead on correct. That should yield about 150hp. Max continuous power is 190hp(3100rpms). So that is running at 79% power(150/190) based on max continuous. I personally never felt I was straining the boat at all. In fact, I bought it with 150 hours and sold it with a little over a 1000. And that thing never gave me any trouble whatsoever. BUT, like you said, the straight 6 is gonna be smoother. Anyway, based on my experience and if I were in the market, I would not hesitate to buy one with the 4LHA in it. Great little engine and probably burn about 1-2gph less. BTW, if you base loading on max output, 2800rpms would be 62% power(150/240). I always wondered how you should base it. Like I said, I never felt I was hurting the engine. AND, I was significantly underpropped. I could achieve 3600rpms on a 3300rpm motor. So I had margin there as well and is probably more important reference engine longevity.
Again, not trying to convince anyone. Just stating my experience!!!
The Mainship Pilots offer great value in their size range. They are handsome boats as well. And the absolute most important thing that people don't think about when buying a boat is...."usability"!!! It is about the most useable boat on Earth in it's size range. The more usable a boat is, the MORE LIKELY YOU ARE TO USE IT!!!!!! It is such an easy boat to handle!! My only knock on them is interior space...and that is why I sold mine. The interior of a 30 is tiny!!! But when my eyes wander from my current boat(which isn't much), they wander to the 34!