Use lead sinkers in the spar to achieve "balance" on the hinges - then use expoxy to keep them there. Then seal with more foam. They will require re-balancing when painted - at that point I will construct a jig that suspends them upside down from the bushes in the hinge to allow a perfect balance - but this is very very close for now (will need to drill out a bit of foam to get the sinkers in!).
