I have just bought a bargain ($160) Summi 50mm collapsible lens for my Leica M6.

I have read that this particular lens is as sharp as the rigid summicron 50mm, but not as contrasty.

So here are the questions:

1. Is this true?

2. If yes, is it the best way to compensate by pushing the film by one stop and/or print with a filter of 3 - 5 ?

Thanks in advance for any answers.