Technobots stock half, quarter and 1/8 sheets of Polycarbonate in various thicknesses
http://technobots.co.uk/acatalog/Online_Catalogue_Polycarbonate_Sheet_103.htmlhttp://technobots.co.uk/acatalog/Onl...Sheet_103.html

I would agree with the comments about kart tyres - they take up a lot of space and are easily damaged. About the only benefit they have is that they are easy to build into a robot.

Ground clearance is a significant factor in combat success, particularly in the UK with the number of flippers. The problem with four wheels is that getting low ground clearance is not easy - the arena floors are never flat, so if you run the robot too low, you will get grounded.

Generally easier (and lighter) to use just two drive wheels and have the front of the robot sliding on the ground.