Lecum said..
Please tell me if I've missed any important issue.

The one issue you may have missed is that the foil mast also works as a fin, keeping the tail of the board from moving side ways. If you ever foiled with 45 or 60 cm masts, you'll probably have a good idea of this. On a short mast, you need to stand very upright, and minimize any pressure on the mast from the side, or you'll experience what very much feels like a spin out.

Kiters can have the front wing directly on top of the mast ("A" position on the Slingshot fuse) because they are always standing upright relative to the board and mast, even when doing crazy upwind angles with the board tilted sideways. Their back foot is behind the mast. But for wind foiling, the foil mast is either at the back foot, or even behind it.

Moving the foil mast forward usually also brings it closer to the mast foot. Windfoil SUPs tend to have a distance around 75 cm between foil mast and mast foot; freeride and race foil boards tend to have more than 100 cm. That extra difference gives more directional stability, and allows for the use of larger sails. It also makes pumping easier. But the shorter distance makes the board more "turny": for radical turns, you'd want the mast between your legs (at least that's what she said ).