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...//...Should the pony be DIN or Yoke?
-same as backgas.
Should the pony be DIN or Yoke?
If you are starting with a yoke reg for your backgas, stay yoke with your second primary reg (on the pony). When you are ready to switch, switch everything to DIN at the same time.
Otherwise, you will be looking at the right tank with the wrong reg, or the wrong thank with the right reg...
...//... I just use what I have, which is a couple of old yoke regs for the pony bottles, while I use a DIN for the main tank. ...//....
The reg on the pony is dedicated anyway as it only has one second stage and no inflator hose.