There should be adequate tension on the locking mechanism for the roof to make a perfect seal against the top of the windscreen. If it's too loose you may find water gets through. You may of course find it's too tight and difficult to open/release the latches.

Both of my Z3's have had needed different levels of force to open/close the latches. My 2001 needs more effort than my previous 1999 model to open/close.

Standard rules apply: if it isn't broken, don't fix it... but there may be a legitimate reason why you need to ;)

Here is a quick note on how to adjust the latch on your roof.
  1. Release the set screw circled
  2. The hook can be threaded in further to tighten the join, or outwards to loosen the join.
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