Okay I'll bite

Due to the low displacement compared to the length of the hulls the accelleration of the flow is mild or even low when compared to far more bulky hulls like freighters. Also the relatively large distance between the hull and the bottom of the body of water where cats sail make the bridge and channel example not very applicable to catamaran hull design. Naturally, these effects are always present but they are often neglectable small.

The depressing of the hulls that is sometimes encountered is far more the result if the induced downforce of the rig then by the suction on the underside of the hulls.

This induced downforce is the direct result of the lift force acting on the sail being rotated downward a bit as the result of the heeling of the platform.

On a certain 16 foot platform a 10 degree heeling of the boat will induce a 26 kg's = 57 lbs downforce when the crew of 150 kg;s is doubletrapped and lifting it's luff hull out of the water. This is about 10 % of the total crew + boat weight.

Often it is very difficult to compute the results of accelerated and decellerated flow around a body and I certainly haven't got the tool at home to do these kind of heavy numerical computations. However, I would be surprised if the suction would produce a larger downforce than the tilted rigw which can easily be 57 lbs.

And there you have it.

Wouter