i came across these...
https://www.woofersetc.com/p-8446-es...onent-set.aspx
however, since i haven't taken apart the X5 yet, i'm not sure if it has a shallow mounting depth or not
lowblock - good idea about the weatherstrip around the speaker... did you run into any problems in terms of the woofer's mounting depth?
taking notes here for my installation.... can't wait to start