On the Cruisair I had to cut holes out on the flat surface of the trailing edge of the wing after removing the ailerons. As far as I know, this is the only way to access the bolt head. :x
Be sure to consult the 43.13 for wooden surfaces. You need to cut circular holes that are bevelled to facilitate regluing the cutouts back in. 8)
:roll: You may be able to cheat, but it won't be easy. If you can get a pair of vice grips on the bolt end and use a open end wrench to turn the nut, you just may be able to tighten them without cutting into the wing. Turn the wrench while holding the bolt still with the vice grips. Bad side- it ruins the bolt threads on the end.
Whatever happens, DO NOT OVERTIGHTEN!!! Tighten until the washer no longer turns, not until it starts crushing the wood :!: