With 3.8v underload, you will want imo, a 306 atty that is in the 2.0 to 2.5 Ohm range. Any lower would be too hot. *some like it hot though.
I hate conventional drip tips... for the best, i'd recommend the Pyrex d/t from Theecig.com... they sell attys too and because they are pyrex, hand made, the fit can vary. They use a Bauway 306 so if you want to be sure, get one.
I bought the d/t and will try with other 306's anyway.
Pyrex is awesome. No juice back in the mouth.