How do I estimate prop & HP requirement?

Note also that fiddling with the Cp or other parameters can have
unintended consequences as the NA's here will attest.
Molland and Lee found less wave-breaking when they changed the Cp
of one of their NPL hull series but couldn't explain why this
occurred sometimes, and not at other speeds. See, for example,
Molland and Lee's report which is available online:
"Resistance experiments on a series of high speed displacement
catamaran forms: variation of prismatic coefficient",
Ship Science Report 86, Feb. 1995, Uni of Southampton.