cg at 25 percent sounds good. i here that if you make the engine level and move the prop forward an inch it will be a more neutral steering and slide in the corners more and less overpowered by the tunnel hull. an inch forward brings the prop to 50 percent of the flat bottom before the hull curves up towards the front.
reports are the hull can handle a 10cc gas or nitro engine if i have it right/ like a .91 maybe. that sounds like 10cc to me. the extra weight keeps it planted on the water for i believe / kick ass acceleration and respectable top speed