Here is the simple box I built.
And here it is in the car.
The box installed is about 1/4" below the floor height. I'll need to ad a spacer to give the woofer clearence to move. so I will raise the height aof the floor by about 1/2". But you can not even notice it when in place.
Lined the bottom of the box with CCF where it comes in contact with the car. But I still need to figure out a way to secure the box.
Open to suggestions.
Box with sub installed weighs in at 30lbs on my micr0-calibrated bathroom scale.