I agree there. I'm against random failures, but if you CAUSE it to fail, fail it should.
Machfly, I've read similar limitations for a number of common engines in WW2 planes. As I mentioned the F4u, which shares an engine with F6Fs, and a couple of inlines I've read about had similar issues.
EDIT: I'd like to see the heat meter spike super fast as soon as you go neg-G... 10 seconds and it pegs red and dies, like you ran out of radiatior fluid or oil. That way you have a little visual cue how much time you have. Of course, time any plane to its historic limit (10 seconds, 20 seconds, whatever).