Judging by the size of the woofer, it would be possible to glass the lower portion only. You'd have to break the 2 door parts apart to work on them. I'm f/g'ing the entire panel on mine, and placing ONLY my 8" in the lowest, most forward position of the panel, and then placing my mid and tweet in custom kicks. Do a search for OBS door panels, and look for a thread I started... That's the most recent postings I can think of, of TribalVision's panels... Whose method is the one I'm copying.... somewhat.
You may want to think about putting the mid & tweets in kick panels as well. It should give you better imaging on your stereo. IMO, if you don't do any mods to the rear of the panels, you should have more than enough space behind the panels to mount the x-overs... Much cleaner look.