@richard.cs and @floobydust
At this point I'm leaning towards it being the shortable coil style, but I could be wrong! The points you brought up about crummy regulators is also an interesting point.
The solder looks okay at least, but I can not check any further as it is epoxy potted and I can not get it out without likely destroying it.
Identifying marks are sparse, but I can see: "2" "TYMPANIUM CORP" "620403" "4990"
Googling reveals this similar product with some semblance of spec sheet. What do you think?
https://www.classicbritishspares.com/products/tympanium-regulatorsAlso, what measurements can I do to test as you suggested, richard?
@skymaster
Hahahaha yeah, right? I love it.
The fly by wire controls are a backup system I decided on to raise the travel limits of the trim motors and raise the speed so god forbid something happens to the teleflex control cables, I can fly the plane home via the trim motors.
It is tremendous fun!!
The EFIS is my own creation, running on a pi 3b+ (well a 3b, i got a b+ to swap in though for more performance) running on processing 3. Which is why it looks like garbage. The screen is a 10.1" 1200nit brightness non touch with a glass multitouch overlay stuck on top.

Still tidying the wiring on the switches on the right! I had connectors on it to remove them (glad I did since I had to twice to shuffle things around)

Here is a custom board I made to run power for everything. On it is an arduino to listen to the rotary encoder and backup mfd hardware buttons, and to run the power supplies. On startup it listens to the power switch, turns 12v and 5v on (for the pi and 12v lcd) and the pi raises a gpio high while the software is running. Then when I flip the power switch on the panel down, it lowers a gpio to the pi and the pi sees that and shuts itself down, eventually powering down and the gpio its holding high drops, which signals to the arduino its safe to cut power.