It shouldn't be a big deal to accommodate a tank as long as it's not too much bigger than the mod that it sits on; I'd just need to know the measurements of whatever is mounted on the mod to adjust the length of the flap and slot for a good fit.
These really do look BA! let me know when the provari one is ready, or the measurements are confirmed... seems that such a nice mod would need one of these holsters!
It looks like the ProVari is .9" in diameter and 4.1" in length so I just need a measurement from the bottom of the mod to the bottom of the button and I can put one together since I already have a wooden form made up for it.