Mark, I have found that all polyester at 385-400 degrees has some shrinkage in it. In my experience, even the stuff that is a sublimation specific polyester and says it is "pre-shrunk" shrinks 3% or so. Therefore, I am still "pre-pressing" or "pre-shrinking" the polyester, no matter what it says!
I have had great success with the tacky paper, HOWEVER, the paper will lose its tackiness if it is too hot or too humid in your printing area and/or shop. I had this problem last summer and had a fantastic conversation with my supplier, as well as the Beaver Paper rep about it.
The solution?
I bought this in order to keep better tabs on what the temp and humidity are in BOTH my printing and transferring areas. This summer, I experimented with changing my hours in order to accommodate the crazy weather I've had here. I moved transferring to the morning (630am - noon) and use the afternoon for printing and outside sales. I'm able to keep my shop at no more than 78 degrees with 40-60% humidity, which I found the paper performs really nicely at. In the print room, I print at 70-75 degrees with 40-53% humidity. Beaver's optimum air temperatures for both the printing and transferring areas is 70 degrees with 50% humidity.
I've found a HUGE improvement in the look of my prints, no ghosting, crisp images, and most of all, the paper STICKS to the fabric!
Hope this helps!