I definitely don't want to be argumentative on this topic but just pointing out that if you use a dip tub as a gas post you will carbonate the liquid faster as you're directly injecting gas into the liquid. This is the same as using an O2 stone submerged in liquid. Surface area is indeed important in many cases (larger surface area to ferment and shallow levels = quicker flocculation than a tall skinny keg), but this is not what is happening in my case I don't believe.
I'll report back my findings when I try to force carb some water off this tank. For the sake of the argument I'll make sure it's full but not up to the gas post.
Worst case I end up with cold flat-ish water, best case great seltzer water and no understanding why a ~7% mead refuses to carbonate under 30 PSI for 3 weeks.