I can beat that. I had to stop a little fast for a school bus (I thought the bus driver was going to let me go by before she turned the lights on but she turned them on at the last second) and my load slid to the front. Since I didn't want to have to climb into the front of the box (topper installed) with good clothes on, I took off a little fast after the bus pulled away. The tailgate dropped and everything landed in the road! That drop in liner was replaced with Herculiner.
I'll get a spray in next time, I'll never do Herculiner again.
One thing to watch out for on the over the rail Dodge liners, they go straight down from the rail to the floor and have a large gap between the bed and the back of the liner. If you cut the top off, there won't be anything holding the liner against the box side and it will probably fall in.
I gave my last 2 away (1 over the rail and one under), keep an eye out, they show up. You could try putting an ad in the classifieds, someone might trade you for an under the rail liner. Used car lots are a good source too.