Anyone suggested at 2 or 3 mistakes high to dip the nose a bit to build up speed then roll inverted and see if you can hold it inverted. If you can hold it inverted without it flicking until it stalls I would think the wing geometry must be near correct. I have found too much elevator for a given CofG will cause a snap in just about any plane but usually when pulling out of upward of downward lines, but I have seen them in straight and level flight with too aggressive elevator moments.
Remember WW1 planes did not do round loops usually they were egg shaped at best and sometimes there was a near stall at the top with the airframe falling out of the loop.
Dennis