The speaker in place with the new upper bracket and showing the wire terminal. They only cost a couple of dollars, are air tight, allow for easy hook-up and look professional.
Yes, that is my blood.
Here I used a drawer slider attachment bracket because I have a few in my junk drawer. Lots of other hardware store solutions would work. Note that when you remove the fuse assy there is a bracket with a big hole in it, and this is in a very handy place to attach a bracket. I slid a speed clip on so a sheet metal screw would work, but a number of solutions would work just fine.
The bolt that attaches the bracket to the box is an ancient VW 10 mm sheet metal screw that is threaded into the MDF. Apply torque carefully! Again, just to illustrate that a bracket is a good solution.
To hold the bottom in, I put door insulation foam peel-off tape on any area that might touch and then some in between that big plastic trunk floor support and the front face of the speaker.
It is all good now on even the deepest sounds, although I do need to put some tension on the access door for those "special audio moments". Heh, heh.