In the 9 years I've been using Epson printers I've done borderless printing often on all of them, 7600 through 9900, and have never had any issues. If you look carefully you'll notice the little "pads" along the upper part of the print deck. Most of those are actually spare pads, in case one of the borderless(drainage) pads becomes too saturated with ink. There are of course only certain roll widths that will accept borderless printing, and once you start you'll see that the pad at the left side of the paper you are using will eventually become inked. Beneath the pads at 10", 16", 24", 36" and 44" there are drainage tubes leading to the maintenance tank. As a matter of fact, if you check the pad at the extreme right end of the print deck you will also notice that the pad there is totally inked, but they seem to drain very well and never cause a problem. If you do see any ink deposited on the back of a roll print near the edge it's likely that the pad has picked up a bit of dirt that's keeping the ink from draining. You can remove that pad very easily, clean it and reinstall. Or, take a pad from elsewhere(not a drainage pad of course) and replace the faulty one. Never a problem in my experience.
Gary