Looking to add options. What about a KR8 xl batt (for length of charge)w/adapter for 510 atty? Would you use the regular 510 atty or mega for that? Also looked at the 901, not sure of mah on that batt as compared to the kr8, or if I can get an adapter for kr8 batt to 901 atty, If so, can I use 901 cartos with that as well? I'm trying to get this sorted out, and you all have been a huge help-gleaned a lot of good info from this forum-but still learning so any and all advice or opinions are appreciated! 