Here are some things you may find useful if you decide to pursue building your own frame.
http://www.chiefdelphi.com/media/papers/1705 - Nice paper on different types of drive train setups
http://www.chiefdelphi.com/media/papers/1682 - Copioli and Patton. Cant go wrong.
http://www.chiefdelphi.com/media/papers/1522 - CAD Help
http://www.chiefdelphi.com/media/papers/1443 - Drive train basics
Keep in mind building a reliable and effective chassis is more than just welding some aluminum tubing together and slapping some motors on. Your chassis is a system that relies on each and every part put into it, and the physics behind them. The kit frame is a well engineered solution, but there are some inherent set backs you will see by using it. Its up to you as a team to decide what is important to you and whats not. Your first custom designed chassis may not be the best thing out there, but you'll learn something by going through the paces.
As the 2007 season is fast approaching, I would not recommend going belly up into a new drive train design. Either stick with the kit frame for another year, or find a team in your area (or online) who will be willing to mentor you through this stage of moving from an inexperienced rookie team to an intermediate team who can come up with their own innovations.
PS - Theres a lot of white papers for different gearboxes and code ideas, but not a lot for fr ames? Whats up with that?