http://www.chiefdelphi.com/media/photos/26312 A couple years ago 703 did a 14 wheel system. I don't think they ever said a weight for it though. I know the upper structure of that machine was sparse and had to use a decent amount of fancy materials.
You are probably familiar with another no-chain-gang, 25. They use a similar approach to you and use larger wheels.
As for cutting weight, what thickness is the wall on that tubing? Going from 1/8" to 1/16" wall cuts the weight in half. You could also probably be more aggressive on your lightening of the gears. Steel is quite dense after all. (This applies to inside your shifters too) And don't forget, sometimes having a lot of weight down low is a good thing.