I've tried most everything, but settled with a plastic crate strapped down in the back. It works better for me than the canvasback type options.

1. My doggy likes it better. She doesn't particularly love car rides, hanging out the window, etc. She just likes laying down and chilling.

2. The crate contains any dog mess. The fur sticks to the crat pad mostly, she drools in there, etc.

3. It allows me to still throw stuff in the back, and keep the stuff and dog separated.

4. It's easy to take the crate out when I need more room, just unstrap the tie downs. I mostly leave it in, though.

5. I also like the idea that she's in her crate if I get hit, or something. Unless it's something tragic, she'll be pretty safe back there, more so than just sitting/standing somewhere in the cabin.

Give it a try.

Also, I just use a large sheet to cover the cargo area, and the middle seat. It's low profile, same color as my interior, and easy to yank out and throw in the washer. Plus, it's cheap. Just another easy option if you won't want to spend canvasback money.