Skin hinges? Do you mean using the covering for the hinge itself? I know a couple pattern guys who do that and swear by it. In fact I'm using that technique on the patter pane that just came off the building board.

Never thought of doing it on a speed plane.

How I was told to do it is instead of making the front of the control surface "V" shaped you angle it ike this "\" from the to to the bottom. Then line it up with the trailing edge of the wing and fip it up onto the top of the wing and apply a 1" wide strip of covering down the hinge line.

Then you flip it down the whole way and apply a strip to the top and cove twing as usual....no gaps and one friend of mine has two years worth or flights on his 2 meter pattern plane and no signs of faiure. It does make a shieking sound when doing snap ros though due to the large gap between the trailing edge and the aileron at full defection.