Got a bit further with the drawing.
Here you can see an overview.
Throttle, with dudleys idea for a lock. :-) Keyboard on drawer-thingies.
Throttles, now angled, on rails.
Dudleys locking mechanism again :-) A wire going to a handle near the seat will be appropriate (dudleys idea again)
..At last, getting it all sorted out. Now i just need to set it up temporarily on chairs etc, to see if all the distances and heights are okay. (and figure out what to do with the chair-lock)