Art,
The best I can do is site a couple previous 395's data. Those boats both topped out at 21 to 22 knots with 5.9 liter 480 hp engines. Our boat will be the first delivered with the 480 hp 6.7 liter Cummins. I have no idea how the additional torque this engine makes will effect performance.
As for recommended cruise, I think that these hulls are quite nice in the 8 to 10 knot range from what we have seen when aboard. We wanted the higher output for those times when we wanted to get moving.
Extrapolating data from the 5.9 liter performance charts, it appears that the boat can run at about 17 knots when the engine is 300 to 400 rpm's below the redline.
Of course we will know more soon!
Bruce