pretty sure the hole needs too be in the same place but one on each side one further would suck air in when the juice was low
You can put as many holes as you like in the bottom of the carto I still don't think the liquid will feed up the wadding enough to keep the 2nd coil properly fed, as I mentioned, the wadding isn't absorbent enough to suck the liquid up even if you took a drag now and left it 2 days before your next drag. In my experience, if you don't top the carto up (either manually or by using a 2nd hole at the top) then the top coil is definitely going to burn more easily than the bottom coil.
My holes are in line with each other so I tend to make sure that I hold the DCT in the right position so that even when the liquid level is low the top hole still gets some liquid, once it's really low obviously that can't really happen (unless you are lying down to vape maybe
) but as I said, hasn't caused me any problems so far and my last carto did 80 odd mls of liquid with holes top and bottom.