Use the tried and true technique of eye balling the airplane from the top, while on the ground of course!?, the axles of the gear should be just about in the same line of the leading edge of the wing, you must prop the tail up for this, so the airplane is in an attitude as if it were flying (horizontal), I've used this technique for over 27 years, on all kinds of airplanes, straight wings, tapered wings, high wings, low wings and biplanes. It works!