We just recently installed a staggered set of 20" TSW Nurburgring wheels on a customers 2013 GT. What a difference!
As most of you probably know already, the Nurburgring is very light weight and strong do to it's rotary forged construction.
On this set-up the 20x8.5 weighs 23lbs and the 20x10 weighs 24.45lbs.
Details: Find TSW Nurburgring custom wheels by size