We certainly have similar arsenals and tastes gear-wise!
I've only shot one roll so far through the J12 and the camera itself, was guessing difficult exposures in dappled light while using 400tx (tri-x) for the first time so as you can imagine the roll didn't come out so nice. I'm not sure how much I like 400tx either...
The J12 is very good value for money, Quite sharp so far and well built - seems to handle flare pretty well.... Only thing is the bokeh seems to get busy looking sometimes, but not too bad overall. I will shell out and get either a hexanon 35 or biogon 35 eventually though, the j12 is okay for the moment. I'll post a result from it from the next roll if you're interested..
Lightmeter... I've been eyeing off the smallest sekonic one - I think it's called an L208 twinmaster or something but it looks very small and light, has reflected and incident. Later this year I'll buy a bigger sekonic one with more features like flash metering for DSLR work though.
I tell you what - that elmar 50 on your m4-p looks great and has an extremely pleasing rendition.. You like it?