Well I cut out the chassis for clearance for the axle and started the installation of the cassette holder on the other side as well.
Here I used a hole saw to cut out for axle clearance

Here I marked the section to cut out to be able to drop axle out thru bottom

Here is the chassis after above section removed

Here's more metal for the scrap pile

Not shown was that I redrilled the cassette holders to reorientate the adjustable cassette 180* for the way it was pictures before.