How does a hole 195mm in "bubble" on a sloping surface on several sides? It is not easy. We must say we were a good hour to talk nonsense with serious errors of geometric concepts, geometry, and then we left we went into action. First, we chose the position of the center tube (between the first and second order, and 185mm from the waterline) inside the hull on the right side, with a laser we found the center of the left side, made a hole with a 10mm drill we did pass an iron pipe 10.
We then cut two circles of wood 185 mm in diameter with a hole 10 in the center and we have placed inside a plastic tube of the same size. We then cut diagonally across the pipe until it is flush with the hull with a pen to mark the diameter of the pipe on both sides of the hull. We got two ovals all crooked disturbing, with the "quick" we cut out the parts and after some tweaking with the flexible tube is fully entered into the 2 holes. perfectly centered and level. Magic. time the entire operation about 4 hours.
Saturday it firmly from the outside dall'inerno and then remove the excess.