I've been researching articles online regarding the effects of rotating mass on acceleration to try and validate at least mathematically what everyone has been saying. Not trying to make this a technical nor theoretical discussion but I came across a spreadsheet that's kind of interesting. You plug in car specs plus specs for two different wheel/tire combos. The end result basically tells you how much more or less torque is used in comparing the two sets. Less torque used to get the wheels and tires moving should mean quicker acceleration. It also calculates a chassis weight equivalent given the weight difference between the two wheel/tire combos. Bottom line...it appears to be saying that you can go as wide as you want as long as you achieve a weight savings with a new setup versus your current one. The magnitude of the gains given a few pounds saved is surprising. How this translates to ticks on a stopwatch, I don't know. That's another story.
Here's the link to that article and its spreadsheet if you're curious.
http://the-welters.com/racing/rotational.html