I have carried my E1b for a long time and loved it's form factor. One day at the machine shop I got bold and deiced to open it up to see if I could get an 18mm cell in there. Sure enough, it's tight depending on the cell but I managed. From there I used it as my EDC with 18350 cells and saw great run times.
I've made many triples and swear every time I make one it's the last one I'm going to make but I find myself fitting yet another triple into this guy. I originally had a 5000K light engine in there (so I engraved the head with the specs) so I tried to put another 5000K light source in. I came across some Nichia 219s that were pretty high CRI but closer to 5000K. In testing the light engine at two drive currents I measured the following with a clear optic.

Low (1A drive into 3 LEDs in parallel) 215lm (OTF) 4911K 87.5 CRI
High (3A drive into 3 LEDs in parallel) 464lm (OTF) 5125K 89.7 CRI

It's a surprisingly pleasant white :-)

I have to finish the head still (driver not in place yet) as well as ad a spacer to my brass tail extension (doesn't always hold the switch in place) but other than that it's a rocket in disguise. Beam shots to come early next week.

Enjoy