Originally Posted by FBinNY

While the axle is separate from the pinion, it isn't simply a matter of drilling a hole through the middle of a standard axle. There are a few important differences.

1- standard axles have rolled threads so the OD in the middle is almost 1mm less than the nominal thread size. The center of SA hub axles has a diameter greater than the ends.

2- SA axles are have side flatted ends to accept a keyed anti-rotation washer. This is a critical feature because the central pinion is the fulcrum for the planetary system, and unless keyed to the frame the axle will spin when torque is applied.

I'm not saying an axle can't be modified to work, or made from scratch, just that it isn't a slam dunk.

Unless a longer OE axle exists, it might make more sense to narrow the rear triangle to match the hub than widen the hub to match the frame.