Thanks for the replies all. I don't have a render, I was just designing in my head. it would be 5" colson wheels mounted by bearing blocks (7/8"), the outer wheels would have a washer under the bearing blocks (1/8"), and then the C-channel (1.25"). It would only be used on a flat surface. The goal was to get the frame as low as possible. The alternative is to mount the wheel+bearing block+washer combination onto the 3/4" tubing we used this year, resulting in the outer wheels having .75" of ground clearance and the inner wheels having .875" of clearance. The wheelbase is about 15" (end wheels are 3.5" away from chassis).

Thanks all for the help!