:+1: Amen, as well you should. 
An additional heat shrink tubing wrap can solve side to side looseness, as can a band of black electrical tape. Very easily solved “problem” to have.
Simon did a good job designing the L6 to accommodate a wide variety of cells. Let’s face it, there’s a lot of options out there and a pretty significant margin of difference in these readily available cells. I’m pretty sure virtually all of us would prefer it this way over Simon designing the light around a very specific cell, like, his own proprietary cell that sells for $15 apiece, so we can pick and choose to suit our fancy. Right?
When it’s as simple as a piece of tape, it’s hardly worth griping about in my honest opinion.
One way to use a magnet securely with L6 and FLAT TOPS
4 x 1mm glued magnet and an xtra-thin O-ring protect from the unthinkable
Works for me. YMMV
+1
Simon did an excellent job on the L6.
This is a difficult problem to solve (using two 26650 batteries in vertical series) given the range of length in many 26650 batteries.
We each can solve this minor problem, even if it is only a problem for me. 
If you’re feeling a little adventurous you can pick up a soldering ‘kit’ for ~$35 (cheap station, flux, and solder wire) and add a solder mound/pancake on the positive of the liito cells adding a mm or two to overall length. Make certain to read about how to do this properly!
Then you’re setup to make some simple, but major changes (driver/led swaps) to flashlights as well. I would probably tinker with flashlights before jumping directly onto cells though.
…and now for the interminable wait between the ordering of the flashlight and the receiving of the flashlight (and batteries).
I would like to see a stainless steel bezel for this light!
The 5200mAh protected battery being sold at ME is listed at 71.46mm, and is longer than the older protected keeppower 5200mAh which is 70.1mm. I have this keeppower battery.
For me I choose not to use the keeppower and choose unprotected batteries that can be used in both single and twin vertical series set up and fits the L6 to my liking.
I ordered more KeepPower 5200maH batteries on 8/2 and my acc’t states that they won’t be shipped until 9/1.
If it helps, unprotected Basen 4700maH cells work fine in the L6.
+1
Illumn has the Keeppower 5200maH protected for $8 ea, they are 71.10mm (L), best I know these are the King Kong’s or EVVA just different wraps.
Calvin also has the Keeppower 4000maH which I have been using in this L6 and the length is the same as these $8 5200maH’s so if the lengths are accurate then they will work.
Just thought I’d mention
Strange. I run the Efest 4200s in the L6 and have no fore/aft play at all. There was a bit of side/side play, but a couple wraps of Scotch Blue 2” wide painter’s tape remedied that.
Now they are “vacuum” fit, with ZERO side/side play, and still ZERO fore/aft play. I can shake it as hard as I can in all directions and it’s as solid as a rock. 
Some of the larger batteries should really start to be called 27700. It's difficult to build a tube that would fit such a variety of different sized cells there are on the market under a single type name, 26650. Same goes for 18650, especially protected. Seems to me that at some point there'll be an evolutonary split between the larger and the smaller cells, each will be given a different designation and go a separate way 
+1
The problem becomes more acute when using batteries in a vertical configuration as in the L6 in series.
The Efest do work in my L6, but I found them to not fit as well as the other batteries I mentioned and that I have been using.
This is really just an issue of user discretion and not one of ‘wrong or right’.
Well holy shit, the 69.5mm Keeppowers are finally available! Too bad I bought a different light in the meantime while I was waiting for these (nitecore TM03).
It should be no surprise that I’m still buying one of these though! lol Where’s the best (cheapest and most reliable) place to pick up the L6 these days?
Cheapest and most reliable, is like jumbo shrimp or army intelligence (an oxy-moron) probably when hell freezes over (another)…. enjoy your TM03 till then!!! 
adir’ , if you do a search using a public search engine for “Convoy L6 for sale” you should find what you want. You’ll need to open up the 5 or 6 hits that pertain to what you want, to compare price. Banggood, gearbest, aliexpress, and maybe ebay and amazon would be the typical hits to look for.
BG is out of stock and say they’ll restock on Sept 1st, their price right now is $55.95
When I bought mine I had a code that brought it down to $47.50 and I just tried that code and it is still good.
I’m fairly sure you have to link to BG through this other site and then log in and use the code but if your interested I’ll pm the info to you.
M4D M4X deals - Astrolux WP1 and WP2 LEP -> Ctrl-f -> L6 -> copy the coupon code and follow the link to pick one up for $47.50 (apply the coupon code at checkout).