I would not use the bars on anything more than a slight uphill. Their advantage is not noticeable under about 18-20 mph (unless you're in a headwind). For the hills, it's more beneficial to be able to breathe as easily as possible and apply steady power to the pedals, that's why all the pro's will use the tops of a drop bar on a big hill. Also, try to get up the hill as fast as you can and allow yourself to lose a little speed at the top for a short time while you recover. You have to balance that effort vs recovery, but the uphill section wrecks your average speed so it's really best to get up the hill as fast as you can.