After the two busy/action days, I went into Mining again for some calmer waters (Mobius Group) and chill out a little.
Found another nice CMDR around in 38 Lyncis and asked if he was interested to try Wing Mining/Prospecting.
Some interesting lessions learned during those ~30 Minutes :
- Collectors still do get confused due to Instancing, but at least they didn't blow up on fragments like they love to do i.e. with bugged Instance Cargo Canisters
- lots of uncollectable but visible fragments (tried manually scooping one - Ship flies right through); "No valid Collection Target" is still a safe indication no actual fragments remain to collect
- still got alot of Metals out of Double-Mining
- both our Games crashed at the same moment after some 20minutes (some bug), so Wing Mining seems a rather unstable thing to do in the Game
(after getting back in game, we were still 350m apart from each other and immediately saw each other - so at least finding the other guy again seems no problem)
Double-Mining observations & tricks :
- 1st CMDR to fire the Prospector i.e. sees 35% Platinum/10% Osmium/6% Gallite
- if the 2nd CMDR fires his own Prospector
after the 1st CMDR depleted OR
before the 1st CMDR started mining this Asteroid, will see a randomized Mineral composition, i.e. now 35% Indite/10% Silver/6% Bertrandite
-> but if the 1st CMDR leaves that Asteroid mined but non-depleted (>0% and <100% remaining), the 2nd CMDR's Prospector will see the same composition from his Prospector
--> hence, double-mining that Asteroid is then possible, both get the same good stuff out of it
Funny detail :
One CMDR's Collector Limpets sometimes try to (and occasionally can) swoop fragments already transported by the other CMDRs Collector Limpets

(especially when they're waiting in front of a closed Cargo Hatch - to allow one CMDR to collect the whole double-output of a single Asteroid)
As fragments are never stolen/illgal, CMDR collector Limpets will happily swoop from NPCs mining in the near vicinity - and NPCs being NPCs... they don't seem to mind *g*
Lazy Miner's Pro Tip :
When NPCs mine asteroids in the vicinity, their mined fragments can be used as "poor man's Prospectors". If they get good stuff and you see it - that's the stuff you'll also get if you Prospect/Mine their Asteroid
And last but not least - after reading it elsewhere, I can confirm that the highest Asteroid density indeed occurs in bright-white parts of an Asteroid Ring.
Much easier indeed due to the high Asteroid density per km.