Before I came to use V4L full time..I bought mods and had 901's. I went and got adapters so I could use Steve's cartos on them. I don't think people with 6 volt enjoy them..too high of a volt.
I have a mod that can do 6V, and cartos with one of the 510 adapters that adds so much airiness (too much for many at 3.7V) is all I can stand on it... and that I sure *can* stand, it tastes great! And I'm on the wimpy side, all other stuff at 6V tastes burnt to me. It's got to be the airiness working to advantage there, IMO anyway! Oh and of course cartos are bliss at 5V!
Ok, I'm an editing fool tonight. Wanted to add, I also tried a 901 to carto adapter at both 3.7V and 6V, and it sure didn't give the same bang. Barely there at the former and not much more than slight burnt taste at the latter. There's definitely room for improvement in the whole area of adapters!