Thanks, @DannyP, I think if I were half as savvy as you at assessing the amount of time jobs will take I'd never have gotten started on this. Last night after dinner I hammered out a piece to shroud the cutout for the gate shifter cable anchor.
I got back after it for two hours this am:
This piece will get rivets tonight or tomorrow. The trick to doing this, apparently, is you have to assemble it with all the fasteners before trying to shape or fasten anything else to it, or else everything that's not what your working on will change shape.
With this little bulb thing on it I made the (much simpler) close-off plate for the back and started on the last two bits of flat bar reinforcement.