Hmm, I'm wondering whether or not the blue wheels are a good idea then, I'm aiming for a tornado-esque design, so I'm wanting as much surface area with the floor as I can get. I do actually have some small tyres at home I scrapped off an old RC monster truck which would fit the bill, but I stupidly didn't keep the plastic drums for templates, how might I go about building a set of wheels? I originally thought I could stick two blue wheels inside a rubber lining, but that might be too expensive and weak.