As noted, removing that tray is a pain...I tried coming up with a way to relocate everything then decided it was easier to leave things where they were.
I found a sub box (dual 10") with a slanted back and just the right height - the amp is on the angled side against the seat back and the whole thing wedges under the package tray. Added a trim panel which gave me a place to mount the cap & main fuse.
Looks like this:
View attachment 60334
View attachment 60335
...with a 12" Memphis in it. It's a heavy pig.