I used a wooden cutting board between the layers of the T and put AK DISigns on the front and back of a shirt. Also for POR! I found doing the larger one first worked best for me. Oh....I used one large and one small DISign.
You can put on as many as you have fabric for it to adhere to. My suggestion is to leave the parchment paper on the first design while you are ironing on the second design. Also, we have found that large designs on the back of the shirt can be pretty hot in summer. They don't breathe as much as normal screen printed tees do. We have started putting the larger design on the front and a smaller name with a couple of smaller designs around it on the back. Happy ironing!!