Update: Still trying to get just enough of my build done to begin capacity testing but feel like I'm getting close now. Having never built something like this before, I'm discovering things take wayyyyy longer than I thought and, of course, life interruptions haven't helped.
Perfect example of this is the amount of time it took me just to get those control wires all hooked up to the side of the SBMS: the better part of this past weekend. Dacian recommends CAT6 cuz it's twisted but CAT6 and the SBMS piece that accepts those are immensely fiddly to work with to put it mildly.
1. CAT6 wire is NOT designed to be stripped, or terminated with anything else but network plugs or push-down tools. It's just too thin. Even with
the right stripper (Hesitant to click that link? Don't blame you! HAH!), it takes multiple attempts to get a clean end that hasn't removed one or two strands. When there are only 6 to begin with, that's a problem. And if you want all your leads to terminate at the same length, then you gotta snip any good ones you've made and start all over to get all 8 wires to the same length (so give yourself plenty of extra length for this when cutting your CAT6).
2. The original SBMS0 that I have (Dacian's got a new receptacle to take those wires in his new SBMS) is likewise not designed to take CAT6 (unless, per him, it's solid core ... has anyone ever seen solid core CAT6?). You have to insert a small pin to open a gate that allows you to insert those hair-follicle thin CAT6 strands and then remove the pin to capture the wire. Was only successful with about half the ones I tried this on and even those pulled back out with just a little tug. The other half refused to go in without just collapsing in the hole. Peering into those holes with a 10X loop (yes, that's what you need to see into those tiny holes), I realized that some had smaller openings than others. Ordered the ferrules he recommends to get around this, but while that stiffened up the wire to be able to force it in, some still wouldn't go all the way home and some just popped back out with just a little tug.
3. Before giving up entirely and just ordering the new SBMS0, I tried slightly larger wires and found that #18 hookup wire is perfect and probably what those holes were designed to accept. I then used ferrules just big enough to accept both the #18 and the CAT6 and spliced them together. (BTW, to get ring terminals on those CAT6 wires for the shunt connections, I also found that terminating them first with an #22-24 ferrule makes for a much better connection when crimping a ring terminal over it. Then tape the whole thing up for strain relief, cuz if you bend that CAT6 wire just a couple times at that terminal, it breaks off).
4. I also super glued DIN rail mounts to the back of my DSSRs. Works really well and makes the install MUCH easier (can remove/reposition those with ease).