I would think that it wouldn't matter, as long as the thing doesn't get crushed in transit. I've talked to (ok, read here that) folks will leave them upside down, or on the side, etc. for days at a time trying to "burp" them to bring them back to life. Sometime with success, sometimes not. I think the important thing is that they stay upright and level when in use, and more or less level when they are not in use. Others will have a different opinion.
Is it currently working? What's the transit time? Can you go get it? When we picked our used one up, it lay on the side for about 3 hours while we brought it home. Worked fine after we got it upright and powered up. Well, for a few months anyway, but that's a story for another thread.