I accidentally cut a leather tab that was a little too long for my acro tab so it was more springy than usual when I realized...if we generally want materials that aren't springy for slingmaking (for consistency and so it doesn't steal your power away) then why do we accept springy materials for the highest point of force on the sling? (release tab)

Leather itself isn't very stretchy, especially the thick stuff, but when folded back on itself like for an acro tab it is actually quite springy even if you keep it short and stubby - especially at high power.

...so I like I said, I went straight to ludicrous! I had some aluminum angle bar lying around, so I cut out some acro-tab sized chunks and drilled some holes for sewing it in place.

It actually works great! It feels a little odd at first because there's almost no friction on the surface of the tab like you get with leather - but after you get used to that difference in feel it more than makes up for the lack of friction with rock-hard stability and consistency in grip and angle. I didn't realize how much variation in grip angle there was even with stubby leather until I spent some time with this.

It's also about 20% lighter than leather of the same size, partially because it's so much thinner (this stuff was 1/16"(1.6mm) thick. And obviously you'll want to make sure all the edges are rounded so it doesn't impale you every throw.

The only thing I would change if I had my druthers is instead of a 90 degree, I might have it bend closer to flat - 60 degrees or maybe even 45. Since when you are slinging the release cord naturally bends away from the tab so that 90 becomes more like 120. But I think that's mostly just because I'm conditioned from a lot of practice with a stubby leather tab that is nearly flat on the cord. It works plenty well as it is, and I don't think I'm going to be able to easily find 60 or 45 degree angle aluminum and I'm not really interested in the variation I'd introduce by bending it myself.

Ahh yeah I meant 45 degrees from cord to tab, so the other direction from your link(think longer/flatter). But I think 90 is plenty fine, just need to give it some time to adjust.

I thought about roughing up the surface, but I think I'd rather have the angle provide the grip so I don't have to worry about slippery or dry fingers affecting my release - which was always a problem with leather.

Wow!  That's a really cool idea!

Kind of what you already hinted at, the only real concern is being hit with metal moving at a very high speed.  But it sounds like this might be lightweight enough to not be a problem.