Disclaimer: The numbers I generated for T-foil lift are very quick and theoretical based on a set of lift and drag coefficients for a slightly incorrect reynolds number (about twice as much as it should be), so they are technically wrong. I believe the drag only takes into account induced drag; no friction, aspect ratio, etc. drag. It is true, practical foil design is fairly different to theoretical design.

The foil I had in mind was 500mm * 100mm. My mate has a higher aspect ratio foil (about 800 * 75mm) on his moth and I'm not a fan of them for boats, too much fluctuation in angle of attack (due to varying speed, yawing, pitching), which high aspect boards don't like in general. They tend to stall at lower angles of attack than lower aspect ratio foils.