I used the .015 Twill on the back over stable core on a 30# bow with a glass belly and you could have used it for a crowbar.
It felt like a 65# glass bow in torsional strength. I did another test using two layers of stable core on the back and it wasnt near as strong as the carbon, but it was very stable... I started using the stable core right under the glass on the back of the limb on 40-50# recurves and that increased the stability quite a bit over running dead center or closer to the belly. Once you get it into the neutral zone in the center it doesn't do much. pretty much a racing stripe.