I have had a number of both wooden and aluminium floor SIBs but recently bought an Excel SD330 flat air floor which is outside my comfort zone. The engine is a 15hp Parsun with a standard shaft ( 18'' from transom to cavitation plate ).
I have so far only had one other person on board with them sitting forward and myself on the tiller. The boat and engine runs as sweet as can be at half throttle but when we open the throttle three quarters to full, cavitation is the result. If I drop the throttle back to half or there abouts, no problems. The venue is a river with very very little flow so almost still and no wave action.
The cavitation plate is approx 3'' below the transom with the upper plate about half an inch above the transom bottom. I have tried each trim position on the motor without improvement.
The boat pressures are .25 for the tubes, .40 for the keel and .70 bar for the floor. I use a Bravo BTP12 to pump the boat up and have found that a separate pressure gauge shows the floor at .60 and the hand pump which came with the boat shows just below .60 bar so perhaps the Bravo is not quite correct.
So far I have not tested the pressure of the floor, keel or tubes after being on the water for a short time which I will do next time I go out. I do wonder if the floor pressure is critical and if the pressure drops after being on the water for a while.
As I have already said, with this SIB/removable air floor, I have no experience so I am hoping that some words of wisdom will be forthcoming.