I've made my own cars in the past. Made a Nitro TC back in the late 90's, Which won races and was better (I felt) than anything you coluld buy until the mini 1/8th cars started coming out. I've got pictures somewhere.....
I also made a TC a couple of years agao, based on a Schumacher Mi3.5, but a lot lighter with lower center og gravity and different flex charicteristics. Getting the bulkheads made in alloy was a bit hard though. Sometimes think of doing another one simlar (not a schumaher though!). There are lots of great cars out there, but none I've bought so far have been perfect!
Mine went through a few stages and picked up good idea from other cars as I went...
