Here are two links as well for stabilizers
http://www.threadsmagazine.com/item/...of-stabilizers
http://www.husqvarnaviking.com/us/me...r_Know_How.pdf
For stretchy fabrics, I would use a medium-weight, cutaway stabilizer behind the design. There are several brands of fusible (iron-on) cutaway stabilizers that work well for knits. Inspira has a nice selection (second link) - my favorite is Inspira Stitch Point Cutaway.