Do you still think the midway hinges with the upward spring load is the way to go? Personally I don't think they provide the right phasing conducive for flight. I can see the spring loaded hinge system working ONLY if there is a mechanical "kick" making the tips go down at the end of the downstroke BEFORE the wings begin the upstroke. The tips need to impart energy to the downstroke at the end of the downstroke, not just rely on passive flexing on the upstroke. This could be accomplished by the addition of a trip lever.
Now I await for you to tell me how wrong I am.