In article , says...
Yes.. be carefull what you cut. If you do open up the protector you
will get rain water on the speaker. I found out the hard way and ruined
an infinity 6.5 midbass.

Come to find out, the window is so close to the plastic, it's not worth
stretching out. There is a considerable opening in the factory plastic
which amounts to the lower half of the speaker. See this pic:

http://www.mikesims.com/nissanstereo/IMG_3353.JPG

I think it will probably be OK the way it is.

What do you guys think?