I don't know about this central hole business. I've been using the 401 for a while now and ALWAYS dip. Manual or auto - I've never had a problem and never lost a battery or atty. The way I do it is fill a 5ml bottle with juice (no dropper), just dunk the atty into the bottle (the bottle neck is just wide enough to fit), invert (you see a couple of air bubbles as the atty tops up), remove, replace empty filter cap and vape away. You get a good cigarette's worth of awesome, consistent, 401 goodness per dunk.
Filling up this way leaves you free to cut off over quarter of an inch from the empty filter caps (to regular cigarette filter length). This shortens the 401 (2,3) nicely and further increases the pleasure of 401 vaping.
Filling up this way leaves you free to cut off over quarter of an inch from the empty filter caps (to regular cigarette filter length). This shortens the 401 (2,3) nicely and further increases the pleasure of 401 vaping.