I agree that
JPSS (JetPro Soft Stretch) is the preferred paper for inkjet transfers onto lights.
The issue you speak of may also be a result of the t-shirt itself. If it is a thicker tee, or has a soft "sueded" feel to it, it may be the t-shirt fibers you're feeling there.
After you've pressed, and peeled your transfer, try placing a piece of parchment paper over the design, and press for an additional 10 seconds. That usually does the trick for me.
FYI - You can find parchment paper on the baking aisle of your local supermarket.
Upon review of my answer, I realize I should add that the issue I was referring to here was the rough feel.