Here's the reasoning...
"When diving doubles, the LP inflator should come off the right post and the drysuit inflator should come off the left post (that way in the extremely unlikely event of a roll-off/break-off while tandem air sharing you'll have something to breathe) and both should be connected on the left... so if you have to shut down the left reg you'll still be able to operate your drysuit valve by attaching the LP inflator to it."
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Personally, I prefer to cross hoses and rig the drysuit inflator on the right. It makes for smoother hose routing, and if I were to have to shut down the left reg all I have to do is rotate the nipple on the drysuit valve over to the left to use the LP inflator hose with it.
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When diving a single reg, I usually use an Air Source as a safe second, so the LP inflator isn't an option anyway, and once again I prefer the drysuit hose on the right for hose routing - 2 left, 2 right rather than 3 left, 1 right.
Rick