Any collapsible lens will damage the meter arm if you collapse the lens. Obviously, you can use one safely if you trust yourself to always remember and not to collapse the lens. Leica stated back in the day when you could purchase "Dymo" plastic label tape, that you must wrap a piece of the tape (it had to be a 9.5mm wide version of the tape) around the outer part of the lens barrel (the part that the lens head slides down on) just under the lens head.