Maybe try using a spray adhesive on the backing itself, so that it adheres to the garment. This stabilizes the sewing surface. Also make sure that you use just one layer of a good backing.
Further to Mops suggestion, you should check out the Embroidery intstruction techniques at the link below, also from Ebroidery Library.
Hugs n roses, Meganne
This is how I hoop fine fabric - Hope it helps. I have had no problems
I use a mesh cut away in the hoop and a couple layers of topping above the t-shirt or sweatshirt. If it is a really think t-shirt I have used to layers of the mesh, too.
I'm a newbie, as well, and just did a couple of T-shirts. I put tear-away on the bottom and WSS on the top. My designs came out fine and didn't stretch. If you do hoop, make sure you are very careful not the stretch the fabric when you do so!
I was just reading this today. It's from a discussion on the Ann the Gran website, under their newcomers question. I haven't tried it this way, but think I might next time.
"When doing tee shirts, sweat shirts or towels I never hoop them. I hoop a stablizer weight that is for the design and then add sticky stablizer on top of the others. The next step that I do is put the hoop on the machine, find the center of the design and then I lay the garmet or towel on top, press down gently and start the machine. This way you are not stretching any of the garmets you are doing, this is also the best way to do tee shirts. The ribbing of the material has to be straight or you will have a design going sideways".
I use an iron on tear-away to prevent the T-shirt from stretching AND a cut-away to support the stitches. When triming of the cut-away leave about 1/4 to 1/8 inch of fabric around the design. If the design is very dense, I float another layer of tear-away under the hoop. You can iron on a tricot backing to keep it from being scratchy. Don't forget the topping, it does make a difference.
Iron-on stabiliser is what I use, or cut away. Emblibrary has a nice list of materials and matching stabilisers, see link.
I also used cut-away. pin it with needles on material in frame. It works. Hugs Marie
If the garment is of stretch material, use cut away, and otherwise use tear away if there is no stretch to the material.
Hi, Go to "Embroidery Library Projects", there you will find help on many embroidery fabrics, by Kenny. H&*.
Wash & dry your shirt first. Shrink your CUT AWAY stablizer by steaming it with your iron. Use cut away, not tear away and if it still puckers, try ironing on an iron on stabilizer before you do the other one! Good luck! Also be sure to put a topper (like Solvy or any WSS) on the top of the shirt to keep the stitches standing up and not sinking into the knit!)