I've had my trunk broken into twice and my custom box, sub and amps stolen once, so I decided to make a box that would be hidden under the floor. I'll just keep a can on fix-a-flat and my AAA card handy for trips around town and throw the donut spare in the trunk for longer trips.
here is the progress so far:
First layer (I did 2 in the trunk and then pulled it out)

2 more layers done

My lovely basement makeshift 'workshop'

Trimmed with the speaker ring in:

The shelf for the amps & power block

Next step is stretching some t-shirt material over the top and epoxying that. I'll keep this updated.