Glad to hear its normal for the knob to be a wee bit loose when lifted.
Though on my M2, its a bit loose when the know is retracted. On my MP, when retracted, it snuggly fit ( no play )
http://www.youtube.com/watch?v=Le6KQ...e_gdata_player
The M2 has had a Wasserman lever for the past 30 years !