I have seen what you mean on the apparent difference in performance in relation to batting amount, but haven't thought about it much. My initial guess is that it has to do with how the gases expand during vaporization. This process is happening in a semi-enclosed shell and perhaps the extra expansion room would have some effect on the efficiency of vaporization.
That's just my off-the-cuff first thought though. I'll take a closer look and do a bit more thinking on the specifics and come back to it.
I noticed the slight differences in battery hole as well (and the slots for that matter). I haven't yet pulled one apart to see what other differences there might be (just got em yesterday!) but you can bet I will. Initial impressions though - these do seem to be performing every bit as well as their hard-capped brothers in everything except longevity. I have no reason yet to suspect they won't perform as well with that too, but I simply haven't had the pleasure to use them long enough to say so.
But I'm working on it right now!!!
