Well I didn't use doubles because there was no point in them for that (and I use doubles either solo or with people knowledgeable enough that it would not matter), but I did use my sidemount rig (only one I have), and afaik I'm not the only one who did.
But maybe you had an actual question behind it, which we could still answer even if we did not lug an extra tank for nothing?
More a statement than a question, Patoux, especially now that I've completed the course -- in sidemount doubles, my normal diving configuration. (Now
that's a bit of a boast.)
My course instructor was skeptical when I declared my intent to do the course in my accustomed rig, and it led to a spirited discussion among the instructor team at the shop (in a resort town in the Philippines). Two of them were set against it, and they would have insisted I use a jacket BC from the shop ... but the manager, a tech instructor who does most of his diving in backplate doubles and a dry suit, saw enough merit in my "train as I dive" argument that he said okay to my giving it a try, and to see how (and if) it worked out....
To that end, we started out in the pool with the "unresponsive, non-breathing diver on the surface" exercise. The task here is to determine that the 'victim' is non-responsive, turn him on his back, inflate his BC, get rid of his (and your own) weights, regulator and mask, listen for breathing, then start rescue breathing while you're getting him (and yourself) out of your BCDs, all without interrupting the five-second rhythm of "mouth-to-chin resuscitation."
Of course I was hampered by my gear -- but not seriously, and I was able to get out of my Katana BCD despite its lack of shoulder-strap buckles ... I did get tangled up in hoses and bungees, a few times, but I was still able to keep the rhythm of the rescue-breathing, while I used the five-second intervals to try again and again until I got myself free. And I got proficient enough to pass the skill, by the end of the course, even if I wasn't as efficient as my fellow student in the dive-shop's standard jacket BC and back-mount single.
So we were all winners here -- me, because I "trained as I dive;" and succeeded in the course despite the harder work of doing it all in sidemount doubles; my fellow student, who learned to handle a side-mount diver in the "non-responsive, non-breathing" drills; and my instructor, who believes he is the first to complete a Rescue student on sidemount, and who is preparing to post photos of my "non-responsive at surface" drill performance on the shop's Facebook page -- even if I showed all the elegant grace you'd expect of a walrus beaching himself on a rocky pinnacle offshore.