Wanted to post another pic of a new light I put together along with some info I found here that might help some other members. It's a Fivemega 18350 E-Series Body with a Malkoff E-Series Tail Cap and Malkoff VME head with an M61NLL drop in.
A Keeppower 18350 works just fine even though it's on the large side. This is my third Fivemega E-Series body. I've had another 18350 and an 18500 but I sold both of those because they didn't see a lot of use. Well one popped up again on the WTS threads so I figured I'd give it a shot with a VME head I had laying around. One thing I see quite a bit on these FM E-Series is that the threads are tight. I have no issues with stock E Series parts but only 1 of the 3 VME heads I have would screw on completely. This is of course without any module in it. Also, most of the Malkoff drop ins do not complete the circuit within the body because the taper is just a little too narrow. I put down 2 layers of foil tape and they worked perfect. Shown below is how I applied the foil tape.
I've removed the head about a dozen times to change batteries and such and it's worked just fine. Run time with the M61NLL and the 2,000 mah 18350 is right around two and a half hours which is great for me. I mainly use the light for walking my dog at night and I have about an hour and a half walk I take so it's plenty fine for me. The knurling, like most FM lights, is second to none. It's very aggressive but I love it. Reminds me of the very early Mags! The only knurling I think is close is LEEF. I wish FM still made his 3P and 6P 18650 C-Series bodies because I would buy the heck out of them.