I was thinking the larger heads like the Hound Dog, Hound Dog Super and the Wildcat. The circumference isn`t that much different between the heads and the Maglite body. I can take a few pictures tonight and e-mail them to you to show you.
Inside diameter of a Maglite `C` cell body is approx-26mm, outside is approx-31mm.
Inside diameter of the Malkoff heads are approx 28mm.
I say approximately cause I`m using a manual caliper.
The threaded part of the Maglite neck could be turned down to accept the Malkoff heads forgoing the need for an adapter but I think that would take too much material away from the neck of the flashlight to be reliably sturdy.
The body would have to be bored out as well for the larger 26650`s (5200mah) to fit a `C` cell mag.
A `D` cell mag wouldn`t need the body modification although I rather like the size of the smaler mag and the `D` cell would need a larger diameter adapter.
I could send you a picture to illustrate.
