Speaking from experience (i’ve soldered hundreds of those things together) those COBs are garbage. They’ll only put out about 70-80lm per watt at real world running temps whereas a CXA3070 or Citizen 1212 chip will get about 130-140 lm/w. I’m actually starting a very similar project to yours, I’ll be using Vero29’s and/or CXB3590’s on my helmet with a slim, bent heatsink and seperate battery pack that I can carry in my backpack.