Sanding can be a drag; sometimes it seems to take forever. Looking good. I hope you get the parts needed soon.
Continuing with the battery box, today I soldered and glued the cable
First I wanted to easily identify the right polarity for the batteries even while changing batteries in the cave using the spare light:
So I painted half of the battery holder in red to mark the positive side :)
Then I soldered the cable (2P1S):
And last thing for today, glue the cable and seal the hole:
I had to glue it instead of using a cable gland since the hole is very close to the edge in order to allow the wires to enter the case below the battery holder.
I used shoe goo because is is perfect for this purpose: bond good to plastics, elastic and waterproof 
Now I have to wait for the glue to cure...
The holders are looking good.
Today was waterproofing day....
I cut rubber seals for the battery box:
And for th head unit:
And glued everything
So again I have to wait for it to cure....
The next step (unless I finally get the electronics package) Is my patent how to secure the screws so I don't lose them while changing batteries, not sure if I can explain it in pictures maybe I shoot a short video
Always nice to see your progress.
I see you have a long weight. 
We call that a BFH Steve. For those times when the LFH just won’t get it done…. 
Hammer is very important tool for caving (less important than light, butt still...) carrying one out of couple hundreds meters dip cave is a doubtful pleasure.
Today I finally started working on the FW.
I used the opportunity to build a third (and fourth) hand after the parts were lying on my desk for months:
Then I solder an Arduino shield with 2 LEDs and a momentary switch to help me develop my costum caving FW for 2 separate emitters:
As usual, programing the Attiny using Arduino was pain in the A** but finally I managed to burn the "blinking" test program
With all that black magic going on I’d lock those helping hands up at night just to be sure. 
Although I already made my own helmet mount, I decided to change it and go for the common GoPro mount.
I bought an aluminium mount but had to modify it in order to fit headlamp instead a camera and also to shorten it in order to keep the light closer to the helmet
Then I had to cut part of the heatsink in order to make space for the mount as close as possible to the body
And the final result
Now I have to drill in my helmet, not sure I am ready for this irreversible step 
3M doublestick tape….VHB
Is it strong enough? I tend to hit my head in rocks while caving (hence the helmet)
There are several varieties. I do not know all there is to know about which one for what job. BUT, the VHB tape is used to hold the aluminum metal panels to the welded steel or wood framework of some cargo trailers. Many trailers use screws to secure the panels, but there are some that have no exterior screws showing. Those are VHB taped. I have used VHB for small projects and it has worked extremely well.
I would have used it to affix the wood skins to my contest entry, but the only tapes I have on hand are too thick. But probably ideal for a helmet light.
have used this one on many things.
https://smile.amazon.com/gp/product/B01BT0A6MG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Nice idea for a mount YuvalS. What did you use to cut the heatsink fins out to fit the mount?
Thanks, I will check it
I took this idea from some commercial lights.
Cutting the heatsink was challenging, I used most of my Dremel bits the most helpful was the engraver
If you do end up using double sided tape, I recommend using a mount with the largest possible area for the tape. It will be much more durable.
Logo’s are attached to car bodies with similar tape, typically 3M. VERY difficult to remove once pressure-set in place. An absolutely clean surface is required of course for the adhesive to stick at full strength.
I think the stuff you guys are on about is acrylic adhesive tape. 3m make the original stuff, though you can buy it anywhere. As DB says, once that stuff gets hold of the right surface, it’s not coming off in any hurry - on the wrong surface it will fall off just as easily lol! It loves plastics, but not oily types ( I don’t mean covered in oil)
This is the stuff , but you can get it on double sided foam too.
I think I will use a glue, so isn't regular (paste) glue will be better than double sided?
In addition, manufacturer recommend not using any glue nor stickers on the helmet, what do you think? Can it weakens the helmet?