One way to solve the stacking problem we use still a new sereis for the actual line but disable stacking on new line. Drawback the process data points hook has to be after the stack hook
alternative approach the special handling of fill is deactivated => line and fill in one step. Advantage: unshift can be used same ordering of hooks as before. Nicer lines because flot first works better than stack first. However not sure why the special treatment was added in the first place....