With the VP-200 boxes located, I need to sling the LSE boxes underneath the subpanel. It needs to be aft to allow knee room (but not interfere with the pedals or brake lines) and needs to avoid the avionics racks. The latter consideration required that I drop the rails at the firewall about an inch. You can see my mock-up solution using a short piece of .063 angle and an .040 alclad plate in the first picture. I've created four of those offsets and will finalize them once the racks are complete.
The racks themselves are .063 angle and consist of 2 side rails (angle down) to capture the boxes between them and support them fore/aft. The forward rail attachment will be to the subpanel. The cross rails are above the side rails (angle up) and are centered on the screw locations on the LSE box.They move the boxes slightly aft of the subpanel by about an inch and still leave several inches to the firewall. The coil connections will be toward the fireall and the D-subs and cooling port toward the panel. I've only done the basic cut and fit; the next task will be to drill the parts together, install the nutplates, and trim the non-mating sides of the angles to 45 degrees. The cross-rails can also be trimmed to clear the avionics racks (similar to the sub-panel) as necessary. Then the units, with LSE boxes installed, can be located laterally on the subpanel and the firewall offset attachment finalized.