I've posted this snap here lots of times now. On the Manky frames we use a 4" length of 2" tube, cut in half down it's length, with tabs welded to each cut surface to form bolt together halves of a clamp. We then add a small tab at 90 degrees to the clamp, which lines up with a similar one on the axle tube itself. These stop the axle turning or sliding sideways in the clamp. The photo shows the front half of each clamp. The back halves are welded to the frame.
I used this system on the GS850 rolling chassis I built for my ex, Rainbow.
http://www.mankymonkeymotors.co.uk/forum/index.php?topic=331.15