To give you an idea of the Leica lenses the collapsed distance it sticks out the front of the camera, minus lens caps or filters is
3.5 Elmar 12mm
2.8 Elmar 21mm
2.0 Summitar 24mm
I'm not sure about the LTM Summicron but would assume it will be about the same as the Summitar. You can get an adapter so the Summitar can take 39mm filters, and I think you can get a slip on adapter to take 39mm filters for the 3.5 Elmar.