You seem to make good progress, Stewart. I admire your approach to get the optimized details out of your car. All seen as a sign of a deep love to her.
I must confess that I‘m not seldom lazy and impatient and a lot of my „improvements“ mean to keep at the stage of a „Gedanken-Experiment“.
Funnily the Gedankenexperiment can satisfy as well, even if nothing changes in the real world. I.e. since two years I want to make a nice leather shroud around the steering column...well...this spring...I hope
Regarding the number plate, what do you think about to quit the plastic mount?
Somehow this plastic mount does not really fit the look of the car. Of course I (or we) get used to it, but...
Keeping the number plate in a quite similar position as now, meaning the same distance of the car, but without the plastic mount, just located only a bit lower, backed up by a stabil but thin layer behind the plate and mounted on such brackets as you have made, and let the plate „breath“ with some air between it and the car, if you know what I mean.
The different versions shown here where the plate is totally below the chrome grill have careful to be matched. Some of the posted solutions look indeed very good in their enviroment, i.e. with badges on top.
But the Mog could also look a bit too „unsporty“ if you know what I mean.
It is also a question how wide the very car is and so on.
I could think of a position slightly more down to let the lower chrome bar of the radiator show but not totally all of it.
So far my Gedankenexperiment
(Do you know this German wording, at least I have seen it to be used by Americans when talking Einsteins theories of relativity...which is of course a much more trivial task than any hypothesis concerning the mounting of the Morgan number plate