Have they been tried? If the rear wing broke the surface before the front wing there'd possibly be an easier auto correction before the slam down.

The advantage of a T-tail is that it is more efficient and thus could be smaller, and decrease the tail drag portion of the hydrofoil total drag. The main foil produces two things that are counter productive for the tail. The first is downwash and the second it turbulence. A convention tail may be only 60 percent effective comparted to a T-tail.

Windfoils like airplanes have a down loading tail. That is in a normal attitude, the tail pushes down to counter act the main foil downward pitching moment. If the tail left the water first the main foil would pitch down until the tail re-entered the water. I suspect this would happen quickly, smashing the board into the surface of the water.

Some windfoils have a bit of T-tail-ness already. The down-angle cradle of the LP FRS foil lifts the stab up about 1/2 inch above the fuse. This is not much, but it does allow for a really small stab, that, I think, is always flying in clean flow, sufficiently above the downwash and/or turbulence of the front wing. This foil delivers a clean ride at all speeds.

Any foil design that places the stab on the top of the fuse (when the foil is upright) begins to achieve this. You want this anyway since it makes the stab push down onto the fuse. It does not depend on screw tension.

One of my other foils has the stab on the underside of the fuse, same side as the front wing. Thus, when the stab pushes down it is pulling against screw tension. Also, it is too close to the downwash and/or turbulence of the front wing to give clean flow when you go really slow and have to increase the angle of attack to keep flying. This foil is really great at speeds of over 18 mph, but gets really mushy and stally below that.

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segler said..
Some windfoils have a bit of T-tail-ness already. The down-angle cradle of the LP FRS foil lifts the stab up about 1/2 inch above the fuse. This is not much, but it does allow for a really small stab, that, I think, is always flying in clean flow, sufficiently above the downwash and/or turbulence of the front wing. This foil delivers a clean ride at all speeds.

Any foil design that places the stab on the top of the fuse (when the foil is upright) begins to achieve this. You want this anyway since it makes the stab push down onto the fuse. It does not depend on screw tension.

One of my other foils has the stab on the underside of the fuse, same side as the front wing. Thus, when the stab pushes down it is pulling against screw tension. Also, it is too close to the downwash and/or turbulence of the front wing to give clean flow when you go really slow and have to increase the angle of attack to keep flying. This foil is really great at speeds of over 18 mph, but gets really mushy and stally below that.

Forces on the stab are minimal, only if you do crazy stuff like jumping you get bigger forces (but those are in the other direction). Plus I cant imagine the disruption of waterflow by the mast is any good for the flow around the stab either. Might be a little better than the disruption caused by the frontwing, but that is not my expertise.