using tubes as wheel spacers?

Well I tried that several years ago on a go kart,. Wanted to put riding mower tires on it for more ground clearance, and the new tires wouldn't clear the drive sprocket on the axle. I did exactly what your talking about, cut a 2" thick piece of wood, roundish, and put longer studs on it, solved the clearance problems, but I suggest you keep a socket and ratchet in your pocket because you'll be lightning it up every 10 minutes

Just a thought, If you took and made your wood spacer, and sleeved the bolt holes with the tubing, just a little less than the thickness of the wood, the wood might compress enough to bottom out against the tubing and keep it tight while giving more support than just the tubing

And before you say anything, yes I'm a hillbilly at heart