I would test one with several different types of embroidery. I would worry about the vinyl tearing away from the perforation of the needle unless the vinyl is adhered/bonded to the terrycloth, versus an actual separate layer. You could also add a layer of iron on vinyl after embroidering them to "seal" the bib - like a patch. Back to the original question, I would use WSS on the top and bottom, as the vinyl should help to stabilize the stitches. Good luck with your project - would love to hear about the results on this type of bib, I have always used plain terrycloth bibs for embroidery.