From memory, my stock 20" wheels with Goodyear RSA were 63-64 lbs. The RSA's at TireRack website show 32 lbs so wheels are 31-32lbs which is pretty normal for a 20 x 8" aluminum wheel.
The other issue not really addressed is where the weight is located when going either larger or smaller. Larger diameter wheels, even with lower profile tires move the rotating mass further away from the center, making it take more energy to speed up and slow down the vehicle.
That's why I went to smaller diameter tires, when I lowered my Flex. While I too prefer a wheel well that is full of tire, I was willing to have about the same space at the top as stock, and be able to use a 2" smaller diameter tire. My adjusted axle ratio is 7% higher (now 340) and while the engine is running 7% faster RPM, my mileage is no different. (less energy expelled speeding up and slowing down mass). On my other set of custom wheels, - ASA AR2's which are 18 x8" and 22 lbs, I run Conti DW's, same diameter as Pilot Super Sports, but different size. They are down to about 5,000 mi left and have shed an astonishing 4 lbs each of rubber! They are not as responsive as the Pilots in turn in, and when it was cold out (40 deg) they didn't hook up really well at the strip. But, haven't had Pilots to the strip so have no comparison as to straight line hookup. Both sets of tires seem to be good for 30,000 mi. RSA's show little wear... but only use them to drive back to IA at Christmas, as they are A/S, and others are only summer tires.
For those that aren't into stripping, and want a good looking light weight wheel to go with stock tires, in my opinion (emphasize opinion) I would be looking at the TSW Nurburgrings. Reason I went with Interlagos is that the other custom wheels I have on my G8's as well as ASA's have a mesh style look, and I didn't want 4.
