The axle uses .126 (1/8") wall thickness. This results in a bend free axle, yet still light weight. It is more difficult & costly to source this material, in 96" length.
Pete Begle has stated he cuts the axle in two, then uses a sleeve, in order to be able to extend the width, & use the same set for 8' Cats, & 10' Cats, like the Tornado.
It is easy to source this pipe on eBay, in 48" lengths, for $14.
If one only needed an axle, this could be made for $28 vs $75-$125