With referance to uneven fuel usage 150/2 172.its not to do with your weight at least not in my view.Might be a bit of out of ballance flight,but not much.Every one of the type I have flown seems to use in preferance fuel from the port tank first,there is a cross feed but it takes a while for it to catch up with demand.Maybe something to do with slightly differing pressure over the port wing,prop slipstream etc.Any other offers???