A couple of days ago I was going to make a shim (washer) from an aluminum pie pan for material but didn't get around to it.
I thought about a wire ring instead, I guess that would be a bunch easier.
I use some Kanthal, wrap it around a needle about one and a half wraps, slide if off and snip straight
through the loop, the ends fall away leaving a nice ring of wire. Make it just a little smaller then you think you'll need and you can open the ring to slide over then
threads, better then being too big to fit. Different size wire makes thinner or thicker washers, a little trail and error will zero you in on what works best for the atty and 510 your working with. Make it bottom out the 510 too much and over time it can mess up the 510, I made that mistake already making them real tight and wallowed out the
threads on a 510 in one of the zbbmod ebay kits. But tighter, without over doing it makes for a less ohms wandering for sure when they fall that low. My next issue was the atty's unscrewing just a tiny bit from handling, in and out of pocket, bumping and falling over, that's when I started snugging the atty's down, now I can rebuild, attach, set the temp and forget it until it's time to rebuild again, no more bumping temps up and down. If my builds were higher ohms I doubt I'd have to go to those extremes to stop the wandering, doubt it would change the temps that much.
I just like nickle, it works for me, I used it from day one once going to TC. Well I started with the soft, Tempered was a real blessing when it came along, I'm happy and comfortable using it.