We saw on your first design how the rear of the box would/may let smaller objects fall out. Can you be a little more specific on how you redesigned the rear section to make it "sealed" unlike the first design.
Nothing could fall out of the first design, it bolted flush at the rear of the undertail. There were very, very small gaps on each side of the rear(sides, not bottom) that I sealed with silicone. Had I been about an 1/8" more precise it would have been a non issue, but it was early in the am when I finished up the first.
The second trunk was only done because of a light rubbing issue with a passenger hitting a deep pothole, so I wanted to try one not quite as deep.
I thought the second time around I'de use a trash can bottom as opposed to the file box. The trashcan seemed to be more durable plastic and the outer corners weren't as bulky as the file box. It was just more simple to drop in a completely sealed box, as opposed to the extra effort it took to make sure the original 3 sided design was a precise fit(inside of the tail itself and inside of the taillight was the rear wall on the original, with part of the box floor folding up and into it, and using 2 of the 4 tail bolts to secure the rear).
I decided on the correct depth(4 1/2", and you actually have more than this due to clearance above the top of the factory undertail's sides).
Then I cut the curves into the front top edge matching the shape of the factory undertail(that allow the seat/hump hooks to move into position).
The trashcan was just cut down from it's original 3' height, the curves cut into the to the front corners, dropped in, and riveted to the factory undertail's sides and it was done.
Make sense?