LeadTurn_SD
Contributor
In the "olden days" when I was certified by NASDS, we were taught that ONLY the 2nd stage hose should be mounted on the right. All other hoses went on the left. This was so, if you were fishing around on the right trying to find your 2nd stage, any hose you found over there was a 2nd stage.
1+.
"Standard" traditional gear configuration has "breathing sources" coming from the right side of the 1st stage, and "everything else" coming from the left.
Modify your gear setup for what works best for you... but bear in mind that many of the "Standard" gear configurations were settled upon for good reasons, beyond "just because we've always done it that way". They were / are considered "best practice" after a lot of trial and error in the "old days".
The example GrandpaScuba mentions is a good case in point.
Best wishes.