^^ I do feel scanning and 3D printing discontinued parts for replacements will become a thing... just as soon as practical ways to do it emerge. For instance, affordable methods of accurately scanning interior plastics, even large pieces such as the SC interior door surrounds.
MLeopard, I can confirm today that you are correct and that I was overly optimistic about fitting three 52mm gauges inside a single 1-DIN panel. I actually ordered the three gauge bezel pictured in my post above which was designed for an MK4 VW Golf radio area (by 42 Draft Designs). As far as I could tell I was dealing with a true 1-DIN opening in that generation Golf so I figured the bezel must fit into my Metra 2-DIN bracket that I've had sitting around waiting to be used.
I think the internal mounting area of that car's dash must be the standard 2-DIN size but the external bezel area the panel goes into is larger than what we have. And as you observed the gauges are very tight in the pictured bezel and not at all easy to fit into your custom 1-DIN frontal area in your CAD file.
Smaller diameter gauges would probably fit in a neat little row but the only way to have three 52mm in that strictly defined 1-DIN space is, I assume, how you did it by staggering them.
You never know unless you try! But now I think I am leaning towards your CAD design for flush gauges below a standard 1-DIN radio.
Or, as another crazy idea... putting the two 52mm gauges offset to the left in a tight configuration and figuring out some other data/readout purpose for whatever remaining space is available even if that is a very common and inexpensive LED voltmeter panel (which would save the need for a 52mm voltmeter gauge). Either that or some non-round LED wideband panel or LED air-fuel ratio panel or a combination of a couple.
I'm just thinking out loud at this point and you did share these for others to play with them after all but that and the staggered three-gauge mockup you came up with I think are great options for this design you've come up with!