Okay, I did get one card to feed through at last. However, the print area was all messed up. This could be user error.
I made a 7x10 canvas in Photoshop and then put the 5x7 photograph on the bottom of that canvas. I then fed the 7x10 sheet in the manual-roll sheet feeder lengthwise, i.e. "portrait" orientation.
However, for some reason the image didn't print correctly on the card. Instead of starting to print right below the crease, on the bottom 5x7 portion, it started to print about halfway down that bottom portion - so only about half the image got printed before it cut off.
From what I understand, borderless printing isn't available with custom paper sizes. The Epson rep I spoke with today confirmed this, but when I asked him if I had to enter any values in the custom paper setup in the Page Setup dialog, he said no.
I'm just curious, for those of you who had success printing cards, what was the margin around your image? Did you enter anything into the Page Setup custom paper size dialog, or did the margins happen on their own?
Finally... I would love to be able to print cards at home. Anyone have other suggestions for how to do this?