All i can add is that I was also bothered by the extreme 'lightness' on my c4s. I added techart springs (and alignment) and like it much better now. Not sure if the alignment alone would have done it, but maybe. fwiw, it still has that go cart 911 feel, just not that annoying 'lack of control-ish' feeling at higher speeds.

So i guess my point is, try the alignment or springs, i think you will like the results... my stock setup sucked (and felt slightly dangerous) no matter how much some will defend it as classic 911 behavior...

 

Wait, you guys are taking corners in heavy cross-winds at 130 mph ?

 

Lowering the car brings down the center of gravity - that will help you. You could also put the GT3 Tek front lip on it - I think that gets you another 20 lb of downforce on the front.