I have an Epson Photo Stylus 820 and used to have a similar problem printing 8.5 by 11 borderless. I found a post on the Adobe forum once that helped me. The guy said that when Espon prints borderless, it actually stretches the image and that results in some of it getting cut off. What I found to work in most cases is reducing the size from 100% to 97.6% and then instead of the image being centered, I offset left to .07 and top to .07. When the print preview comes up, I enlarge the preview and examine the edges to see if anything is getting cut-off or if I am getting white space. If so, I adjust further but typically these settings work for me.

Good luck.

Barb