I know that low weight is good however, as is this frame is not going to be overly light considering that there are 8 wheels and all of the chain and such associated with that. This year our drivetrain weighed 75 lbs and we are trying to cut that down considerably without losing too much strength. With our current drivetrain we were never out-pushed so I am using that as a basis to work off of. Also I think it is better to be underweight and be able to strap on ballast than be too heavy and forced to cut weight. I have posted a new version of this drivetrain
http://www.chiefdelphi.com/media/photos/28328