Spit blackout VERY easily. I agree with that. It's worse than N1K2 for sure. The reason why the George blackouts very little at hight speeds has to do, IMO, with hi-speed control. N1K2 becomes, as you point, slow motion at hi speeds. Over 300 kts. IAS, it rolls very slowly, and elev authority is also reduced. So it is difficult to pull high G's when moving very fast. I think Spit elev authority is better at high speeds.
Pretty much all of the faster planes in AH can cut into a N1K2 at higher speeds (+300), and that's the trick with fiting against George. If the faster plane manages to keep its speed over 300/350, little the George can do. Besides that, over 20k, N1K2 can do nil.
Cheers,
Pepe