It seems to me that the reason lightweights & middleweights are cheap to build is because these classes havent had much attention. One can build a heavyweight with cordless drill motors, however you need to spend a bit more to get a competitive heavyweight. The reason a heavyweight costs more is more due to the popularity of this class than anything inherent to the different weight limit. To put it another way, if there are no other competitors, Psychosprout would be the undisputed winner.

Id rather see new leagues of the popular weight classes than fragment all our efforts into different classes which cannot easily compete against each other.

No disrespect is intended to those who build lightweight and middleweight machines - Im sure quite a few middleweights could take on heavyweights and win.

Colin, any chance of a parts list? It would be useful if we put together a how to build a robot page.