A flat hull will definitely give good forward speed, but without bevels it will be very skatey. Bevels are best known for allowing the board to release from the water easier, BUT, their lesser known characteristic is that they are also very important for providing directional stability - i.e. moving in a straight line. No bevels and a totally flat hull will be very hard to keep moving in a straight line, especially when pumping the board. The end result will be that the board will skew left or right rather than move straight. The greater the angle of the bevels (i.e. the more vertical they are) the more they help with directional stability, but too vertical (100% vertical = no bevel, or, a normal surfboard type rail) and the water wraps around the rail and will prevent release.
But then again, what the hell do I know? If I could build my own boards I would also try to buck the design trends. Respect to you!!!!!!!!!!!!

Thanks Dommo!

This design wouldn't work at all for a SUP, where directional stability is an important design goal.
But for a wingfoil I don't mind if it's skatey on the water.
The SUP was a good starting point for wing board design, but it's already diverged and will keep doing so.