Just my 2 bits but I've always ran either 4 bias or 4 radial.
Bias plies usually have a stiffer sidewall which when coupled w/ radials on the back, "COULD" screw w/ the stability of the car.
But then again it's just my 2 bits.
I'm still running 14" on all 4 corners but I think over the winter I'm gonna have to bite the bullet & look at a larger wheel. I was thinking about going to a 15" but if tires are dwindling like the 14" then that may not be the route to go.