That is all fine and dandy but are you sure your trim is right once your up and riding? Do realize that once your moving there is more drag on and more wind placed on the kite so it will set deeper and you will need to trim it more.
You can all so use your board to push the kite forward in the window. So here is something you can try instead of constantly playing with your trim strap. Edge really hard and get your board speed where you feel comfortable, bare off/downwind unhook, edge and pop.
Trim the kite to get it to fly at the proper angle of attack. Use your board to control your speed and the power.
P.S. Overpowered is not being able to control your board or keep an edge. So no you can not unhook in those conditions.
First thanks for the advices...second, bare off/dowind while riding or just before/to unhook???I think to understand that you're saying to push the kite forward while riding ( =ride more upwind you can keeping enough speed ) if you're very powerd isn't right???