I seems I didn't make myself clear in my previous post
I'm not saying you use less G for performing a loop in a slower moving aircraft, but it's much easier to put more stress on the aircraft when you are faster.
My point was actually about the truning radii you mention. You'll pull a lot more G in a faster moving aricraft for a small radius trying to stay inside the box than in a slower one. Much more than 5 G in my Pitts doesn't help much anyway, I'm just wasting energy...
Light aircraft, slower speed, tighter corners.