really, if this is going to be your go fast bike - you should really go narrower than 700x28 at some point. Really, skinny tires are fun and less work You also get used to them.

I wouldn't put 26"ers on your gunnar - I'm slightly prejudiced towards 700cs, because I hated the one 650c bike I had - and at 5'1, I fit fine on 700s.

There's a ton of 650c vs. 700c threads on here - and really, just decide what you like If gunnar can do it for you, a few people on here have bikes that they can swap in between 26" and 650c tires on them depending on what they're doing with them.

There is a lot more selection available in 700c tires than 650cs, you're more likely to be able to bum an innertube off of someone during a century... (I don't know if sag wagons carry 650c tubes or anything like that). And if you were touring on it, you'd have any easier time getting 700c or 26" tires or tubes or replacement wheels...