Fitting protected cells will be a problem, probably impossible on the twisty version unless I can build a recessed tailcap with the spring set back from the contact plate that makes the connection to the rear face of the tube. From the rear face of the tube, to the top of the 7135s on the driver, is only 2.71", 70mm cells measure 2.755" or so. It would fit with nearly zero clearance with a single-sided driver with no components on the battery side, but I don't have any like that. 105C converted to single-sided won't work, as there has to be a total of 12 chips, and if they're triple stacked they won't fit in the pill.
If anybody absolutely must use a long protected cell (though when the driver has low voltage shutoff, I don't see the point in a single cell light, kinda like being upset your new Ferrari doesn't have provisions for a trailer hitch) you may have to wait for tivo532's DIY east-092-style driver, which is single-sided. The 'real' east-092s still exist somewhere but they're mixed in with big batches of the low output copies, and I don't know how to get real ones without buying 100 and sorting through them, maybe ending up with 10-15 that are usable, and a whole bunch of leftover junk.
This is the space left at the tail with a 65mm unprotected cell...
...using this longer-style small spring...
I will have to use the short version of the small spring on the driver even with an unprotected cell to leave room for a compressed spring in the tail.