Interesting point. Certainly the Bloodknot's g-recording meter only recorded Nz (correct term), but whether that is the chicken or the egg is anybody's guess this many years down the line.
I'm still in touch socially with the RAF Engineer who brought the type online in the 70s, although he wasn't on the certification side. I'll pick his brains next we cross paths and see if he's any idea.
Bending a mainspar during Cooper Trophy competitions is arguable a way to lose lots of points! I take it that you didn't win.
G