For 'cheap' power plank making - the balloon route from Castle Wars over to the lumbermill is the way to go. You can even chop your oak logs at Castle Wars as there are a few oak trees just the other side of the bridge. Wear your duel ring and carry a willow log, money and 26 oak logs. you will also need to get your weight down as lw as possible - so thats bots of lightness, penance gloves and spotty or spottier cape.