Just a quick question; but why does your car now sit a bit high? Surely it sits at exactly the same height as before if you have the correct tyres on?
His ride height has probably changed a bit because it's easy to go for the wrong (but acceptable) tyre size when upgrading to larger wheels, here's a couple of examples to give you an idea;
Let's say his original wheels were 205/50/16, the total diameter is 61.14 cm
He then goes for GTA 17" wheels with 215/45/17 tyres - total diameter is 62.53 cm
or as is a common choice 225/45/17 - total diameter is 63.43 cm
less common choice would be 225/40/17 - total diameter is 61.18 cm
in the case above, the 225/40/17 tyre is closest to original spec diameter, it will not change ride height (well actually it will by a fraction), but all the others are much larger diameters and will thus raise the ride height (215/45 by approx 7mm) (225/45 by approx 1.14cm).
The larger diameter choices will fill the arches out more but will also raise the ride height