Bingo!
You provided the winning answer!
And what a sad answer it is.
Yes, friends, Larry Pina was wrong when he said this...
The copper inside the SE & SE/30 Main Wiring Harness (leading from the Analog Board to the Motherboard) is in fact 22AWG — the same thickness as the Macintosh 128K Wiring Harness. This is a travesty due to the fact the SE and SE/30 have "Expansion slot" ability, which means they will draw more power in an upgraded state than a Macintosh 128K ever would.
Thankfully,
@zigzagjoe mentioned here that there is a pre-crimped wire solution, so I ordered these yesterday to try out:
I never noticed this shocking revelation before because on most of my wiring harnesses, the printing on individual wires is worn off. But I took a magnifying glass and inspected multiple harnesses this week, and I found the 22AWG printing on them. Ditto for the 128K harness. So it's not a guess on my part. It's fact. A sad fact.
People with a stock SE or SE/30 will likely never care about this, but anyone with a beefed up SE/30 will.
My plan is to swap out the two +5v wires and 3 of the 5 ground wires (two are twisted, so I won't touch those), in order to boost the current handling capability.
However, that doesn't help my Micron Xceed Harness though. The upside to that is the wires Micron used are 18AWG, which is nice, but I am still getting noticeable voltage drops anyway, when I have the Xceed Grayscale kit (with MacroColor 30HR video card) and the Daystar CPU-socketed 50MHz PowerCache accelerator installed.