The first time I'd ever heard of sidemount the only configuration-specific harnesses being produced for the market were the Golem Gear Armadillo and the Dive Rite Nomad. Both of them huge, beefy motherfuckers designed for large tanks and lots of stages.
I tried them a couple of times and felt like I was (pun only partially intended) swimming in gear. Just hoses and inflatable bits and buckles bloody everywhere. As the predominant sidemount instructional technique - at least in Florida at the time - was, "There, now your tanks are on your sides. You'll figure it out."
It took a long time to figure out.
My own first sidemount harness was this POS that didn't fit me properly and, even if it did, it would still be a POS. Uncomfortable, oddly proportioned, inflation in all the wrong places, not really made for/by cave divers. It was just a thing that would hold your tanks, roughly, to your sides. More or less.
And I was trying to make it work with AL80s. Which, as sidemount goes, is on the trickier side.
Steel tanks, you see, just hang there. Like lumps. Once you've got the bolt-snap tail length just about right... that's pretty much it. You clip them on and swim.
80s? If you get the boltsnap rotated 5 degrees off... if your tank band is a centimeter too high or too low... if your bungees are a fraction of a (I dunno... what is force measured in? Newtons? Sure... let's go with that) a fraction of a Newton too tight... or any number of dozens of other variables are the littlest bit off...
You'll have a miserable dive at worst. One tank will be pointing out at a silly angle that you'll have to see cast as your shadow for the whole dive at best.
Nelly did not like the era of figuring out how to configure a sidemount harness properly. Because she had to be part of the experiment as I modified and moved and tried to perfect. More or less in the dark, through trial and error. Nelly prefers that things just work properly instead of having to futz with things incessantly.
Eventually, however, I started figuring it out. Between Nelly and I, two wildly different body shapes, I figured out that what worked for me didn't work for Nelly and vice-versa.
Over the consequent years, now, I've worked with a LOT of different people with lots of different body shapes. And I've twigged onto, more or less, what works for various people with their varied variegation.
To the point where - to toot my own horn a bit - when I'm setting up a brand new sidemount harness for someone I can get it within shouting distance of properly fitting with just a little bit of time and a tailor's tape.
Yesterday, after covering academics, theory, gas planning and matching, and getting things sized we got in the pool, student wearing sidemount for the very first time in their lives...
And the tanks sat EXACTLY where they belonged, perfectly horizontal and flush on the sides.
While Sam (student) floated perfectly motionless in four feet of water.
This is going to be a nice week.
I love my job.