I've been doing some experiments with Cp and Cm

I have been tweaking the specs for my Ger/CS/1905 scout cruiser and the "Super-fast" battlecruiser to maximum speed. For the battlecruiser, there is the 70,000SHP/shaft limitation that has an effect. I thought it odd, but the lowest Cp doesn't give the highest speed. This is close to the best that can be done:

At Displacement=30949.2 tons
Length=804.0 ft
Beam=87.0 ft
Draft=28.2078 ft
Cp=0.61
Cm=0.9
Cb=0.549
DLR=59.5498
Wetted Surface=79812.8 sq. ft.
B/H=3.08425

At speed of 35knots power is 223938.0 SHP
At speed of 36knots power is 258375.0 SHP
At speed of 37knots power is 301770.0 SHP

actual speed for 280000.0 SHP is 36.4983 knots

I've wondered if optimizing Cp and Cm would be a worthwhile exercise. I would iterate over two ranges, looking for the highest speed for the maximum SHP.