Your 36 weighs 16,000lbs right? What will the 39 and 42 weigh? Will even quad 350s move them fast enough? Wouldn't you need at least 60mph to keep up your reputation for speed? Why not Cummins 8.3s, two speed transmissions and shaft drives for the bigger boats?

The 36 doesn't weigh 16,000lbs... I don't really know why or how the rumor got started.
The red boat that I posted pics of weighs 11,600 no fuel.
the silver boat that Powerboat just published the test on weighed about 13,250, but that boat had a lot of extra seating modules and a big t top.
The 360 Cabin model with gen and AC typically is around the 14,000lb mark.

The 39 won't weigh much more. It wouldn't surprise me if the speed is the same as the 36.
We just received the 39 deck ring and liner from the CNC shop. The HUll mold has been here. The first layup will be done shortly.

The 42 will be offered in several configurations. Initially it will be shown with outboards. We plan to look to integrate small diesels such as the 6.7 cummins into the boat. The larger diesels are very, very heavy...

These lighter boats typically don't need two speed transmissions... I didn't see a real benefit.