Two 4 series carriers makes the most sense.
For me, personally, I don’t see why we don’t just have a dedicated 8 cells. It’s a search light, it’s gonna need run time to be used as it’s designed. There are perfectly adequate cells available for very cheap monies, no more than $40 for 8 really good high capacity cells can be found easily. This would have the absolute maximum effects, delivering BRP without a hiccup. (Balance, Runtime, Power). I bought the extension set for the TK61, ran 8 cells, didn’t have a problem with it. That was a much higher current light and it worked out fine.
As a comparison factor, the battery tube with proprietary cells for the TN42 is about $70, for the proprietary battery pack alone (4 cells)
While I do like the IDEA of everyone contributing on the making of a light from the ground up, I’ve seen repeatedly where it’s not sound business practice. A team should get together, decide the parameters, have the light made, then offer it for sale. To me that ensures optimization, without long delays in argument while ideas get tossed around like a beach volleyball. I’ve seen the open thread idea hold up multiple lights and even kill off a couple entirely. Seems funny that people are willing to get upset because they didn’t get what they wanted, but Nitecore, Fenix, Surefire, MagLite, Thrunite, Solarforce, EagTac, ArmyTek, SupFire, Olight, 4Sevens…. they build what they want and offer the lights for sale, they don’t take stinking polls! And most of us here have those brands, never had a single bit of input on how they built the light.
Diversity can build strength and character, it can also break the core, polluting the purity of the concept. Field of Dreams said it , “if you build it, they will come…”
If you build it right, they will come in droves!