ok, i have that radio set up, it was the same for the 575, and Bluey already has a HUGE! fibreglass arm.

if i get the drawing now, i come up the front of the jib, through the head and this wire then goes one side, it tensions the sail.. currently i have another line at the top between the jib top, and head which tensions the sail, the pink line stops at the head and the sail is connected to the line with hooks. ie it can move along the line. i guess bottom tension comes from the front mount at the moment, with the winch at the rear.

Still no joy finding the keel yet. but im going to a display for the weekend, there should be a tradestand with CF tube the size i need, wasnt any in the LHS today. it'll also give dad time when he gets back from London to sort through his cr&p and find it.
if not i laminate up some ply and balsa, and fair in a fishing weight ( streamlined of course )

now.. i guess theres some equation of where the boat should balance on its side when correctly balanced. bottom of the mast? top of the keel?

Thanks for all this help