[nathan_hui]

Keep it simple. The chassis is not the most complex part of the robot, but it is the most critical. Your choice of drivetrain will drive the chassis design, followed by your choice of control system mounting and manipulator mounting. If you don't have a set of guys familiar with stress analysis, I suggest you stick with the Kit base. There's nothing wrong with it, you just need to be a bit creative at times. If you go for a welded aluminum chassis, overengineer it for now until you better understand the forces on the chassis. We've used 1" and 1.5" extruded U channel from McMaster (1/8th inch wall) and haven't had a problem with it, aside from the obvious (or not so) problems from welding. I've never worked with sheet metal, but I don't suggest you try that just yet until you find some people who can work with you through the design of that.