Staggering the tire sizes has been done many times, even on some cars from the factory such as the Corvette. As long as the larger tires are in the rear, you are OK. The main problem I see with doing this is that you can't rotate tires front to rear. So, if you have alignment issues or wear problems on the front, you will chew through tires with no place to put them. The other thing I see with the tires you have is the fronts seem pretty skinny compared to the rear, not that doing that is a problem it just may appear a little funny looking to some people. I personnally like to see some big tires on the rear, but like to put as big of tires on the front as possible (more of a road racer look than a drag racer skinnies look).