It looks like I need to trim off about 1/4" off the lower left tab in order to fit this panel between the longerons.

Trimmed. Fits now.

...but of course, this means that now the part is about 1/4" short so that it misses the outboard row of holes to which it is to be riveted to the bulkhead.

Match drilled through the set of holes along the inboard edge of the bulkhead.

Decided to make a little doubler to extend this tab so it will pick up the outboard set of holes. Found a little piece of scrap .032 thick material. Looks like it came from one of the stick cutouts in a floor panel.

Joggled that piece, match drilled to the inboard set of holes, then added a couple more sets of holes to attach it solidly to the sub panel. Also, for the inboard set of holes, I drilled two more halfway in between the existing ones.

Here's a photo of the tab extension with the sub panel on the bench. The little joggle worked out pretty well. Because the lowest hole of the inboard set of holes was quite close ot the bend, I didn't try to pick up on that hole.

Later in the evening, I used a unibit, snips, and files to cut some slots for the gooseneck arms.

First fit of the gooseneck arms through the slots.

The slots aren't quite long enough, so they gooseneck arms are holding up the front of the canopy frame weldment by about 1/8". Need to extend the slots a bit.

Extended the slots by about 1/4" so now there is some clearance below the gooseneck arms. The slots need to be made somewhat wider. I'll probably shoot for about 1/8" on each side.