You need to find the sweet spot as far as bar position is concerned. usually its about halfway. getting flapping wing tips means you are depowering to much. Speeds like to be parked more that worked.
My advice. downloop to start get downing fast, park the kite, find the sweet spot and feather the bar, Do little micro signs up and down.you don't want the kite pointing upwards. keep it side on in the parked position moving the kite up and down a very feet at a time.
You need to concentrate on board speed. retaining as much as possible. That's how it the speed will generate power. loose your board speed and loose you power.