I've made a start, with wedges and the jig. When I was working with HS93 a couple of years ago, he was raving on about a gadget called a wixsey (I think). I paid little attention at the time, but recently it turned up in some bits and bobs I didn't sell for him. So I had a play with it today, and wonder how I have managed to survive with out it!
Using this little gadget, I was able to measure the angle inside the hull at 10 degrees, then made some wedges for inside the hull. Ive done a cardboard template for the jig, so the plan is wedges and blocks in the hull, pre drilled so I know the holes are straight vertical and true, epoxy them inside the hull, use the jig to position the rudder tubes, that I have to make from brass, turn over hull, pour resin in to fill all the nasty holes etc, and lock the rudder tubes in.
I want to try and make some sort of chamfered end in the tube for an o ring to sit in, hopefully these will not leak. If anybody knows a better way, shout up! Thanks to all comments, its nice to have a conversation going, and thanks to mods for merging the topics