I appreciate that it was built with 5+1 and not 6 or 7+1. I would actually consider building a single cell light with probably 3 or 4 +1. Even 2+1 is ok, and so is FET+3 (higher moon).

The reason is this: Once the battery gets too low to support all the 7135s, every mode between 1 and N 7135s becomes unregulated anyway, even levels that could still be supported if there were fewer 7135s. That's because it's still using all of them, at full power, and just PWMing them. It either can support them all or it can't. If it can't, it dims continuously as the battery continues to drain. You still have some of the efficiency advantage of least not PWMing the FET, (Edit: Nah, even that isn't true at that point).

I prefer a light where I could just set it at say 500 lumen level and it will last there until it can't. To me, the right place for that level is probably about whatever can run for close to 3 hours, so maybe a bit over an amp, and certainly not more than it can thermally sustain. But that's personal as each user may have a different opinion on how long they need to use the light before recharging, and it's easy to desolder a 7135 on these drivers. Of course this is an advantage of buck drivers, with the downside that they don't direct-drive very well.