In low speeds the thrust and efficiency is pretty good. I can foil at 1600w in apx 18kmh with 90kg rider, and a huge foil wing. In higher speeds it’s not very efficient, but it’s capable of about 35kmh. We lowered aoa from 5Degrees to 3 degrees and made the sections slightly thinner, which helped in higher speeds seemingly without decreasing low speed thrust/efficiency. Prop diameter=142mm
Prop distance to walls is important, we use 1mm (max2mm as our 3d printed is a bit off).