The 1616 has a 10 bit adc but it may not matter if you are using an op amp. The little bit I have read about the two series claims very fast adc conversions and a more powerful cpu. Either one would be an improvement on the old 85.
My biggest concern is the attiny could be spending too much time on other tasks and not spending enough time on the boost converter. If this thing works and the switching speeds can be increased it opens the door to higher power versions and maybe buck boost as well.
Its impressive that you have got it down to 18mm. Is there a reason you dont want to go double side?
This design could easily fit 17mm if you stuck some of the smaller components on the oppisite side. Just leave the center for positive to solder on a copper stud or small spring.
In time, I think Aundril will be adapted to work with boost. There’s a few members working on it.
17 mm is considered the most common, across the board. But I've been seeing 20, 21, 22 mm's pretty often lately. Going smaller, AA size, 15 mm would be the next smaller size, I would consider AA size. But of course there are exceptions to every rule or assumption .
17mm is probably the most common as Tom E said. The easiet way is to make it as small as you feel comfortable working with then just change the pcb size to accomodate different size lights. That way the driver can fit many lights just by changing the pcb size in the design without having to go thru the process of designing a new layout.
I do not know any popular light with e-switch and 17mm driver. Why go small? Better change host with more space ;)). Tomorrow last hope. I will get FET with same specs only more powerful as is in original Tamagoshi schematics.
On BLF any light can become a host. There is plenty of lights out there that use 14500/AA with e-switch and a lot of 16340 lights also. Its your design, you design it as you see fit.
I have a Ultratac A1 using this driver with a XHP50.2 making 2000 lumens with a 14500 very floody. Its not a e-switch but I could have used a Sofirn SP10S, Thorfire TK05, or a Utorch UT01 for a host if the driver had been eswitch capable.. A XHP35.2 might be interesting in one of these host.