I am converting a deck to a boat lift. I have 8x8 sqaure pilings built at deck height, 2.5 ft above water. I knew it might get converted into a boat lift so they are all in the correct location. But I need to splice/add appx 12' vertical to the existing pilings. The joint will be below the deck height and will not show so asthetics are not an issue. Current choice is cut both pieces as flat as possiible and bolt metal plates on the outside. But I have also considered dowels (which would need to be 2" dia.) or would be interested in some other type of joint. Realize as far as tools go, that any joint will have to be cut into existing pilings about 1.5 ft above water level.