Awsome! And since it is said that the new ARC head will fit the same battery tubes as the PD, this will work for the new ARC too! The new ARC head is nearly identical to the PD but only shorter.
I would love a 18650 tube as small as possible with no switch at all (just a flat bottom). With the new ARC head, this would be a KILLER light. Probably one of the smallest 18650 powered lights around and would have the versitality of the ARC electronics. I can't wait!!!! Imagine a light not much bigger than a AA light but with runtimes of nearly 3 times that. MAn it would look cool too.