question

First of all, good job reading the manual before install, that's a (unfortunately) somewhat rare occurrence!

But yes you're correct, the permissible battery mounting methods for all Smart Lithium batteries (except the 12/330) were updated in the manuals ehhh either late last year or early this year, I forget when exactly it was. So, indeed, a lot of slightly older admonishments of NOOOO it's absolutely forbiddennnnnn (more than a few of which were posted by me, LOL) are in fact no longer accurate.

Personally, having taken these batteries apart and seeing how they're supported and baffled inside, I would not myself mount them in any position other than upright unless it was a static installation like a house or garage; in a mobile installation I think that over a matter of years the odds of a mechanical failure inside due to vibration would be significantly higher when mounted on their side or on their ends than when mounted upright.

That's just my own assessment, though - at the end of the day, what's in the manual is indeed what's supported by Victron and if such a failure was to occur within the warranty period, you'd be covered!

Thank you. That makes sense to me. And as I’m installing in an Airstream travel trailer, I think I’ll keep them upright.