[Aussie Mike]

the number you should be concerned with is the rolling diameter.

The profile figure is just a percentage of the tyre width. A 225/50 series tyre has a sidewall height of 112.5mm. This is 50% of the width 225mm. It's only approximate and can vary a little between manufacturers but that's how it works.

Your rear tyre is a 45 series so it's side wall will be 45% of the width (245 x 0.45 = 110.25) that's only a whisker different to the front.

I'm running 45 series tyres on the front and 35 series on the rear but the sidewall heights are the same:
315/35/17 315 x 0.35 = 110.25mm sidewall
245/45/17 245 x 0.45 = 110.25mm sidewall
This means the rolling diameter is going to be the same front and rear.

I think Joe's comment on new cars with mismatching profiles not looking right is an optical illusion created by the wider rear rubber making the sidewall appear smaller. I also think the newer Corvette runs 18" rear rims and 17" fronts which adds to it.

Cheers