i just obtained a shrinker/stretcher to play with. i'm making outer rockers for my 33 humpback panel from 16ga. steel. the tool has specs for 20ga. stainless, 18ga. steel, and 16ga. aluminum. would it help if i heated the flange of the rockers before i used the tool to shrink it ? this does NOT need to come out perfect, just the basic curve to match the bottom of the truck. TIA.