I think it will line up if you're strict on the grid. Just place the front/back with just the same amount of space on every card. Do it like this in photoshop:
http://www.yourdesignforums.com/atta...1&d=1205432703
print.jpg
By the way. The red is back, grey is front. Line them up like this. Print front first. Put you paper back into the printer and print the back.
Edit: Crappy thumbnail. You understand the deal anyway.