I used dye cut printed opaque transfers on these. I pressed at 220 for 12 seconds. They did not melt or deform. Customer was happy with them. I tried stretch vinyl first, but the small ribs caused the vinyl to pucker. that would not work. I then used an opaque printable heat transfer. I left printed black vinyl in between the letters so it was more less one large piece. It did not flex and acted as a patch would...meaning the fabric did not stretch where the transfer was. The rest of the material took up the duties of stretching and it all worked out fine.