I somehow missed it….
WOW. The smallest light with tail e-switch and Andruil?
I don’t have the Tool AA Ti, but I can’t tell you that putting a H17F there will be a near impossible or eventually impossible task.
The driver is 17mm, and the pill of the AA normally takes 15mm drivers, that sometimes need to be “shaved” on the sides.
If you look to the description, CRX used a 15mm driver. Not sure if it fits “right on” or if it needed some tweak!
These drivers from LT have those “wings” on each side what makes them more difficult to replace and use in other lights, so calculate the dimmensions well before attempting the mods, or you’ll end with a damaged driver.
If by smallest you mean “slim but not short”, I’d say this may be the “smallest” 
This is a terrific job 
I wish that Lumintop would do one of these versions that the “pseudo copy” of the FW3A, as they are dooing :weary:
I mean by volume.
Actually the driver is 16mm across the wider section of the driver and 15mm across the narrower direction. I had forgotten how close to the edge of the driver the six AMC7135’s are on the bottom side of the h17f though so I am looking for an alternative atm . Initially I built a 15mm mtn fet+1 driver for my Maratac AA twisty which originally uses a driver that’s the same shape board as the Tool but without the ability to use 14500 batteries. Problem was the fact that at 15mm it was too small to make proper contact with the battery tube when turning on and changing modes. And because I had to isolate the ground ring, it flickered and ran terribly. I then removed the driver from the Tool with the help of a little heat to soften the glue and installed that into the Maratac; which is a very nice Improvement indeed. The 15mm fet+1 works in the Tool because the ground ring makes some contact, albeit not much since the battery tube isn’t really holding the driver down since the ID of it is very close to 15mm. I planned to try to use a 17mm driver with enough extra batt- and ground ring surface around the edge & under the solder masking to file it into the shape of the stock 15mmx16mm somewhat oval Tool/Maratac driver. After taking a closer look at 17mm drivers, so far I haven’t been able to find something that will work. Either the components on top are too close to the edge or not enough meat on the bottom batt- ring to take a mm off on each side. Might just have to try solder the 15mm in.