Steve, I'm still trying to figure out your "weight high" CG thing and the "rocking/rolling pendulum action" you're talking about.
The boat has no higher CG then a typical vee. The engines were still in the same place, the tanks were still in the same place and the floor height was the same.
The boat rocked less than any vee bottom simply because the floatation was 4 feet farther apart (basic pontoon theory). It ran like a vee because it was a vee (37.6 Cigarette Race Boat) and it ran a little slower because it was heavier. No mystery here. Simple physics.
Did you need to run it with the tunnel clean, yes, because just like all cats, at certain speeds in certain seas the tunnel will slap.
Most 38 Cigarettes with 440's ran basically the same speed as them because it is a 38 Cigarette! That would be mid to upper 60's.
The 39 Cat ran 72 with 400 Merlins and Arnesons. The difference being that it could cruise at a higher speed. I propped it at 68 tops because it gave me better all around boating usage.
Just like any boat, after your first couple of hundred hours of operating in open ocean with one you will figure out the finer points of it and be able to run comfortably.