You get more of a return from stiffening up the platform, than removing weight.
You can't state that without including some quantification.
I'm quite sure a F18 that is 50 kg lighter and only "invest" a 1% loss of stiffness is going to be faster overall then the regular F18.
There is always a balance point to be found somewhere. A point where the effects of one change are not enough to counteract the effects of another (but linked) modification.
Wouter
