Digital BW, The Print

This is probably a question for Roy directly, but perhaps others have experienced this 
issue.

I'm using Quadtone RIP 2.0, by most measures getting excellent results on my 2200 with 
the new UC curves. There's some microbanding still, but I intend to experiment a bit more 
with the settings and my choice of papers. (It disappears, only to re-appear... I haven't 
gotten as methodical as I should be with this problem.)

My question is about something altogether different: it seems that no matter what I do, I 
cannot seem to get even margins on my prints. It's forgiveable some of the time, but when 
I'm printing, say, a batch of 6x6" images on 8.5 x 11 sheets of paper, the off-center look 
is quite noticeable.

I've tried creating various paper sizes with fiddling with the margins, and I've also 
manually gone into the print location settings in Photoshop's "Print with Preview...." dialog 
box, all without much repeatable improvement. I've resorted to enlarging my canvas in 
Photoshop and moving the live area of the image itself within the document, which, as you 
can imagine, is very time consuming. I print a test image and then go back into Photoshop 
and use the arrow keys to nudge the image left or right.

I'm wondering if this is just a limitation of the GIMP driver? I have no problems centering 
my prints when I print other documents through the Epson driver.

Thanks in advance for your help, and thanks too for your great work on this product.

John