Be careful opening the tailgate if your tarp dips and fills up with water.
I am reminded of the Temple air show some years ago when a buddy, who's own truck was down, used my Unimog as his vehicle for the weekend.
We had one of the usual frog-strangler rains overnight, and though the Mog had a tank tarp covering it for the storm, there was no center support over the bed, so the tarp just sank into the bed and filled almost completely with water. I don't know how much, but it was enough to make the back of the truck hunker down. Gallonage would likely be measured in hundreds.
Anyway, he decides to drain it by opening the tail-gate.
I said "Um, Jeff.... that's a
lot of water..."
He says "I'll open it slowly".
Well, it didn't happen that way. He was knocked on his tail by the sudden rush of Moggie Falls, and was sitting on the ground completely drenched in short order. He was a bit grumpy until he dried out.
Cheers