printing post cards

[tj]

I am using inkscape to create a post card size,3.5hx5.5w, image and then print it to that sized media on a Konica Minolta PagePro 1335W printer, with no luck. When I print it puts it the lower right hand corner in portrai, not landscape as needed, of a letter size doc (test it on letter size). But, the printer feeds releative to the center, not the right hand side and it needs to move to the top, not the bottom.

Inkscape allows you to send through an app, so I put
| lp -o landscape
and it then prints the card in landscape, but still in the lower right corner, but I'm ahlf way there.
So then I try:
|lp -o landscape -o page-right=185
which I thought would move the right margin over 2.5" and center the print.

But, it didn't move. It was in landscape, but its position did not move.

Why didn't the right margin work?
Am I doing the right thing to get my desired results?

tj