Upon inspecting the threads of my protege (because i have noticed a bit of difficulty on battery switches)... here is my 2 cents take it for what it's worth.
The ID thread on the tube is Really Really shallow. But there is a nice chamfer on the id of the tube that helps threading. The Cap's OD thread has no lead chamfer (Really crucial in threads) but has a full set of threads.
To change this would create All kinds of problems for puresmoker, and would probably not happen... the threads would cut through the current size tube, increasing the tube wall would increase the price... all kinds of bad demons would just pop out for PS.
But, because I'm just about dead set on using protected batteries, I plan on actually remaking the tube and end cap at my friends shop once I can source out the right walled tube in SS. Which wont be cheap, and I'm sure the thickness of the protege's stock tube reflects this. I plan to get something thicker walled and a bit larger on the OD but still small enough to bore the Correct ID for the switch housing, then turning the OD and threading for the adapter. Lastly boring the other side to a slightly larger ID so the protected battery will have room, yes bore right up to and create a shoulder where the switch housing would end which i assume is slightly smaller than the diameter needed for the protected battery. lastly i would have to thread the end (this is where the thicker walled tubing is crucial) so that there is a FULL /\/\/\/\/\/\/\/\/ thread there with a nice lead-in chamfer (the lead-in chamfer is supposed to be cut deeper than the threads). then create a new end cap with matching threads and bore the hole for the spring.
Hopefully i could end up with a protege that the OD of the tube would be the same as the OD of the adapter. I'm sure I'll run into problems on how to make it flow like where the adapter hits against the switch housing.
on a good note wow 510 attys work nice on the protege.
if anyone beats me to the punch on making they're own improved protege tube i'd love some pictures and/or thoughts.
PS. MMMMM Chipotle just had that the other day... the barbacoa, black beans, rice, scoop of pico de galo, scoop of the HOT sauce, extra corn, and some lettuce in a burrito bowl.....
(just had to rub it in haha)