I can tell you have an interesting opinion. Unfortunately, with kindest intentions, I think it's lost in translation.
I'm not sure what you mean by the DRIS decomposes into many parts. I've disassembled mine for cleaning and it didn't seem like an excessive number of parts to me.
I think the main problem with the twist on lights is you really have to get in the habit of backing it off a good amount so that pressure won't activate it at depth. Once you get in this habit, it seems fine to me.
I am interested in why you say especially to avoid XM-L T6 and U2 bin emitters. Is the battery runtime too short for your needs? I don't do overhead exploration diving so it's not a concern to me.
Point is that you can distinguish between primary light and backup - on the contrary you can dive with two primaries lights - simple enough. If you know DIR style diving you know that
there is emergency scenario where the diver with failed equipment go foward or go between divers with equipment that functioning.
On other side I look on a backup light as little reliable lamp with sufficient autonomy with cylindrical sizes diameter 40mm and long about 200mm nothing more - it and attach the chest
strap and hide under the armpit - I do not want the shape and size of the Blackjacks ;-)) which is also not balanced.
On powerside - XML is big die it consume a lot of current and need good thermal path ( U2 and T6 are top bins , they have lower inner resistance and goes instead of 3A up to 5A ) in
practice, this means that no restrictions trashed 3xC size battery in about an hour and a half . It also need large optics or reflector in size of 60mm diameter so in general is more more
suitable for primary light . By contrast, the XP-G2 just right, it has enough light right amount consumed and requires a smaller optics suitable for backup.
You can read more on candlepower forums about differences and surface emissivity of different die sizes.
Problem by twisting (turning on on depth ) is IMO in size and shape of thread between head and body. Metal laps have very fine thread ( I have on my GS-35 M30x1,0 with minimum ''
crest'' )
http://www.mechlook.com/wp-content/...rm-Dimensions-for-Standaard-Screw-Threads.jpg
but plastic lights have mostly much larger thread with larger helix and trapezoid style thread ( because of plastic injection moulding that can simpler maintain the prescribed
dimensionsis) that are not so sensitive on pressure.
