Did your handling suffer from 20 inch rims?

The trick is to get a rim with the same offset and backspacing and weight as the factory wheels. Once all dynamics are the same then handling should almost stock, it will differe a little bit to do weigh distribution. Yes traction can suffer from lower profile tires

Well, the OEM 17 x 8 wheel is 21 lbs. and I think the tire is somewhere around 27 lbs. Let me know if you find 20's anywhere near that weight. For instance, I like the Steeda Spyder wheels in 20 x 9.5 chrome, but they are 30 lbs. each.

my aftermarket wheels weight about twice as much as teh stock wheels and I personally noticed no difference in handling...then again I don't push my car that hard in turns, yet enough to know it didn't make a difference with my personal driving style.

Well, I've had my 20's for three years now - let me give you some thoughts:

I did my 20's at the same time that I did the FRPP handling pack.

The ride became more harsh...but I expected this. The trade off is a car that hugs the ground and has no dive (meaning that it does not lean) when pushing it into a corner...and with the FRPP handling pack and 20's you CAN push it in the corners.

Yes, the wheels are heavier...this will slow your 1/4 time and will cause your brakes to wear more quickly.

Traction - I put BFGoodrich KDW 2 tires (summer performance) - so traction is much improved over stock (due to the width of the tire and compound of the tire).

Above everything else listed above (and something that was a factor in my decision) is that they look awesome...!

Hope this helps.