[fsstnotch]

Honestly... i don't think your straight line would suffer at all. Maybe a normal car, but you are running a cobra with a 427R! You've got more than enough power to overpower the 17's and the 15's. In a straight line, I would seriously doubt you are using up all your 427R power. Where if you have a 300hp mustang, it's using all it's power to run a straight line. Add larger wheels and you lose like .1 in a 1/4.

On the other side of the spectrum, you will handle MUUUCH better!