Not sure why you would want to deliberately under-power this vessel. It really requires a minimum of 2 x 150 hp and more would be better. Its sea-keeping and ride comfort will likely be much better on a plane than at displacement speeds. It will likely be fine, and handle properly, at slower speeds, and you could run quite happily at 7 kts (probably on one engine, at < 2,000 rpm). At 10 kts you are likely running inefficiently, and uncomfortably, and you might as well get it up on to a plane. But you can try all this out with the existing engines. Not sure that these vessels are any heavier than they need to be. Jack Angus 1994 42' Zeta Custom Planing Powercat "Bluebottle" Victoria, B.C., Canada