The grip levels front to rear will be very different. In the OP's case, what is 7/10s or 6/10ths at the back, well within grip available, will be 11/10ths at the front, past the grip available.
With 4 Ultra High Performance tires, then under-steer is an issue only when pushing very hard. With All-seasons up front and Ultra High Performance in the rear, the rear will grip beautifully, and the front will plow on straight, at a lower than anticipated speed.
Still, I'm thinking it's not a concern for the OP.
And FWIW, I've experienced under-steer and over-steer on the street. Plus there's emergency situations to consider; having all-seasons on the front just kills braking performance.
Does this same logic apply to a staggered set up?
2001 Mustang GT - Crashed (Other person's fault) Stock.
2003 Mustang GT - Sold
Lowered, Flowmaster catbacks, CAI + Tune, 5% tint all around, American racing wheels.
2005 Mustang GT - Traded in
"Performance" spark plugs and ignition coils, 5% tint on back 3 - 20% on front two, 20 inch silver AMR wheels
2011 Mustang GT - BEAST
5% tint all around. 2014 GT premium wheels. Roush axleback