My understanding is this adapter for the 510 works perfect, but adding the 901 adapter to the 510, you will need to drill a hole on the 901 adapter. Check out this video below.
YouTube - Cartoimizers with the 510 battery
I don't think so. In the video he is using the 510 to 901 adapter. That gets the male thread - to - male thread worked out. Then he is adding the 901 to cartomizer adapter. That gets him the air hole (built into the adapter).
If you just take the small 510 to 901 adapter and cross-drill it, you should get the same result as my adapter.