Eric the 18650 tubes look great. The Mcgizmo 1x123 pack is nice but for the larger Ti 38 head I think more people will go for the longer tube. The 38 would look a little off balance with the short 123 pack.
Your tube design looks great! I'm still in at the proposed prices for a complete light: tri-led 38 head, 18650 body, all in Ti. Three Crees or Rebels please, or whatever your planning is the best combo using your heatsink etc. Hopefully the latest emitters available. I am getting more excited with every new drawing you display!