okay, thanks for the suggestions. my idea was to use Scotch tape (tesa movie haha) but since i had some transparent book foil flying around i tried that first. And it works!! Now both of my E09's work again, and i can tighten the upper head part as strong as i want to!!!
My very first idea was a combination of Tipp-Ex (for the sides of the mini PCB) and a circular cut adhesive foil ("foil ring") to fit into the reflector seam, and the Tipp-Ex works really good at the sides as expected. But it's easier and more straight-forward to drop the Tipp-Ex completely and cut out a larger square from the adhesive foil with a hole in the middle and fit it over the LED dome.
The cut out square should be anywhere between 5x5mm² and 6x6mm². The green mini PCB's size is 3.5x3.5mm².
Verdict:
Now knowing and understanding what can go wrong with the E09 (when you take out the rear spring, when you screw off the upper head part and rip off the reflector from the PCB) and that it is easy to exchange o-rings, lenses, reflectors, i am growing fond of this little serial-numbered thing even more.
It's unlikely that the lens would ever break with normal usage and drops. If the E09 is attached to your keychain or keyrings and you let it drop, the lens will not break, i am sure.
And if the light doesnt turn on anymore, then we know already why: it's because of the rear spring (if you've ever taken it out before. otherwise not.) or because of a short (short circuit) due to the compromised insulation, as described. Then you fix the insulation, as described, and your light is back on.
The head is massive aluminum .. great as heatsink.
The beam pattern (=the reflector) is maybe kind of a lottery but most likely not. I am so happy with my beam pattern ;)
It's definitely built like a tank!!
The major missing part in my review: runtime measurements with Eneloops and with Protected 10440's (and qualitative description of the brightness regulation).
I would ask you guys to help me with the review and provide some RL beamshots and wallshots (or comparative beamshots, in comparison to iTP A3). I dont have a digicam, so please provide some shots for this review thread, thanks!!