One thing I wasn't clear on in the originoal post was weither the flipping was occuring when taxing, or when on take off roll? If you're flipping when taxing, and already holding up elevator, then you are doing it right, you just need to do more of it, more up elevator, less rolling friction (bigger wheels, axle alignment, etc).

If it's on take-off, it may have to do with elevator timing.