2.5 hrs. continued work on the sub-panel.

These should be plenty stiff and strong enough to hold the ADS-B/transponder.

Rivnut installed with Loctite 277.

Both done.

The mounting flange I fashioned.

And it's installed.  Very strong and stiff!  For me this was easier than trying to connect to the firewall since the firewall is covered with soundproofing.

Nice!

Now on to the mounting of the VP-X.  Using my sheet metal bending machine... ;-)

Two brackets for the front.

And let's make brackets for the back.

Bent to shape...

Front with real box in place.  The box will need to be spaced a bit below the sub-panel to make room for the rivet head which will be done from the bottom up to mount this bracket.

These need to be stronger vertically (they could bend), so I'll bend up the sides to make it strong in both dimensions.  To be continued...