I’ve ventured off the standard path a bit by hanging my pony on the right, but my setup sounds similar to the OP’s so I thought I would chime in.
I have a Scubapro Classic BC with an air2 (on the left). My analog SPG is also on the left (the hose and console clip to a D-ring so they don’t dangle). My primary (on the right of course) has a 40” hose. I sling my 19 cf pony on my right side. That way I have easy access to my air2 and spg on the left. The pony does not interfere with my primary regulator and both the first and second stage regulators of my pony are just inches below my chin. It would only take 1-2 seconds to begin using my pony if ever needed.
I began using a pony last year when I went on vacation with my non-diving wife, and I was diving in the mornings. I did not want to count on an insta buddy for air if needed. Now I just like the security of having redundant air.
My 19 year old son is my dive buddy. I’ve told him if he ever needs air, to give me the OOA sign if he can, but get the regulator out of my mouth and don’t go chasing my air2 or the pony tank air. I’ll figure that out quick enough.