Man, I gotta go get some of those, they look perfecto.

Where is the box going you have built?

 

Regarding the silicone: I don't know or really care if JL's cones are specially treated .. they're too damn expensive But IMO it's always better to play it safe .. "Silicone adhesive has acetic acid which is released as the adhesive cures. This acid will corrode speaker baskets if the speakers are reinstalled before the silicone has completely cured." .. do they treat their baskets too?

As for the wood/glass sealing .. I like the fiberglass idea too but honestly you lose air where the speaker is mounted .. so the difference is probably nil to near nil.

Drilling holes .. small pilot hole, widen top, drill in. .. see halfway down here: (also where that acidic fumes quote is from)
http://www.bcae1.com/spboxnew2.htm

Better general car audio informational page: http://bcae1.com .. lots of reading to be done for the full blown enthusiast.

 

I finished with a second bead of silicone during lunch time today. Had my head stuck therough the hole with a flashlight! Anyway, I let it dry for about 8-9 hours before mounting the driver, hopefully that's enough time. But I think my brain got a little corroded from smelling those fumes with my head stuck inside the box ;-)