Best input voltage for R2 drop-in from DX?

[KDOG3]

I have another one on the way and I'm wondering what voltage input ( as in number of regular CR123a's ) will give it the most output. I see a chart someone made for it on the DX website but I'm not quite sure what to make of it. It almost looks like 5-7v is best according to that chart. I'm trying to decide on a C2 or C3 host for it. I just hope I get a good tint. I'm so tired of puke purple......

 

[MrGman]

It will make no difference in the brightness, just the runtime. Pick what format you like the best.