I'm trying to block the back piece of a sweater. It's a 100% wool yarn. After soaking it in lukewarm soapy water, rinsing, and squeezing as much water out of it, I lay it out on a towel. Problem is that when wet it's so much larger than when it was dry. So do I pin it down so that it lays flat or do I pin it down at the final dimensions that I want it to be when dry? Or maybe I re-pin it as it dries?