2 reins with martingale. HELP!

It is a long story but basically, because of recent events, I have decided to try my horse in a 2 ring gag. I read somewhere that it was good to have 2 sets of reins when riding in a gag. One set attached to the large centre ring of the bit (to act as snaffle) and the other set on the lower ring (to act as a gag when necessary).
The problem is i'm not 100% sure on what to do with the martingale? I rode today with it on the top set of reins (the ones attached to the large/ snaffle ring) with the 'gag' reins underneath and on the outside.
It felt okay and he went really well with the new bit but I didn't feel like I had full control through the gag rein. It feels like it should be on the inside of the snaffle rein... but then the martingale would interfere! Help?

The martingale should go on the snaffle rein.

Thank you, that's how I had it :)