Nice box, but did you think of the (ultrasonic/radar) alarm detector which is behind the recess in that panel?? That angled part in the middle of your new box... 
That's part of the reason I didn't take the wood fascia outside the 'cubby hole/parcel shelf' area, the wood face has been cut around the protrusion - the part of the box in front of the alarm I have made solely from fibreglass and left relatively thin (about 3mm) - tho of course I've had to put the speaker spacer ring on now too
If I have to, I'll turn up the sensitivity, but don't really want to go down that route as I couldn't get the shelf out at all when I tried a few months ago (seemed to be stuck in place

) so it would be a right PITA getting to it (and I wouldn't want to risk making it too sensitive so it goes off if I leave the roof off (it's already a bit over-sensitive))