Good on you for trying new ideas. That 'expert' at the shop should have known this has been done for years. I would suggest that you also place a strip of stabiliser from side to side in the hoop, to help prevent the stitching pulling the fabric in at the sides. It happens with heavily stitched designs. And yes, you can also get different types of wash away stabiliser, also sticky back ones. check out Jenny Haskins website and blog - all will be explained.