I have made a little more progress, with the help of several members here in the forums that have given me advice.* I'm learning as I go, so a lot of the woodworking leaves a little bit to be desired in terms of appearance, but it is airtight and extremely strong, so hopefully I can hide most of the imperfections when everything is carpeted.
Just wanted to post a quick picture update.* Yes, I know the amp is upside-down in this picture.* The cables were too much of a pain at this point, and I couldn't find my hex keys to remove them.* There is a bit of a reflection on the ceiling of the vehicle.
Click to enlarge.