Just another friendly nag..I've been looking at another one or two 510 PTs, plus a pair of 'em for my M401, but really, I'd as soon not buy a POS.
I like the 510 PT, with inline battery (hey, nice add-on idea for your PT, just an inlined battery box, USB in and out, no cables preferably..supply with a short standard USB to mini USB for the 'new' connection from comp to it, then plus in the USB PT directly into the box), but the damned cable length and non protection on the cables (really thin) is *really* making me hesitant to buy another pair of them (I di have one currently).
Likewise, the M401 PTs seem to be utterly disposable and auto only.
I'd much rather buy 3 PS PTs with adapters, and....perhaps as a second additional idea, after this one is shipping, it should be possible to make a sealed auto PT of sorts.
You already have the 'battery end.' Leave it sealed. Instead of screwing on an atty directly to it, screw on a 1/2"-1" long diaphragm sensor, for your 'auto' action. All the diaphragm/sensor needs to do is close the battery contacts on your sealed PT 'battery,' and pass through the juice to the atty. You can sell them as 'semi-disposables,' meaning as they're disconnected from the battery, they can be cleaned in alcohol and should live a reasonable lifetime, likely much longer than any normal e-cig battery does.
Take a look at the manual switch 'cylinders' on the KB I believe, for a somewhat visual.
Just a thought.