I'm making lycra covered elastic dance belts and wanting to make one belt to cover two sizes – they're being rhinestoned so this makes it more economical for me. The 30mm and below knits are absolutely fine but the 50mm is much firmer (not surprisingly) and I just accepted that until I removed some from a ballroom skirt made by a Coventry dancewear company. I've had a few different ones from eBay to Empress Mills but none of them are as stretchy as a piece I took out of a commercial dance skirt waistband.
Any suggestions? Actually any tips on how to relax the stretch of what I've already got would be of interest too!