The story behind the prototype sledge goes like this. Lake Harku has always some ice sailing entusiasts on it. But also people who know everything about anything. But still not much useful information you get from this kind of conversations. My oponents claimed that the shape of the board and stearing system is something that you never figure out by yourself. My point was that it is absolutely irrelevant if you want to try the speeds on ice with your windsurf gear.
The main issue is that you have something solid under your feet and skates fitted in parallel. And parallel is the key issue. If you have good parallel you can have huge speeds even with your old dinner table or other furniture you find. To prove that theory I took Euro pallet, put the quality skates in parallel and almost beat those guys with top speeds. My point still is that windsurfing on ice is extremey fun and it is not complicated at all. Critical issue is to get proper skates and mounting them in parallel.