The only awkward thing I find with the 1:2.8/50mm Elmar is that as the whole lens turns when focussing, the aperture index dot also goes round to where you cannot see it! This also happens with the f/3.5 Elmar and f/2 Summar I have for my lllf. The summicron wouldn't do this I think. But then if you are shooting wide open it would not matter. I like the little focussing lever on these 50mm and 35mm lenses.
The lens hood will fit anything with an E39 front, (the earlier lenses being A36 though need slip-on hoods).
If the compactness is so important, perhaps you should be looking at a screwmount camera rather than an M series?
I agree with Darko about not selling - I wish I still had the Summitar that came with my lllf: I sold it when I bought the more compact Elmar!!