I have a 70lb Lab who loves road trips, but he struggles to settle in the back seat of my F150. I’ve tried a hammock-style cover, but he still slides around. Any tips or products that worked for your pups? (Bonus if it works with trucks!)
If everything else fails, consider engaging an animal communicator to find out what he thinks or if he has any suggestions or his take! 
Do you mean like a restraint or something? I use this harness for my girl; it’s crash tested and highly rated. It’s great.
I have seen a bunch of ads on Instagram showing a hard-sided base with a hammock setup. It’s flat and padded and covers the whole back area. I just did a search on Amazon using ‘flat car dog seat’ and they popped right up. Check it out to see if it might work.
I have a hard bottom hammock that I used stick-on Velcro to put carpet on (used dollar store door mats). This makes the surface less slippery and the dogs have better grip. I then give them blankets and they’re good to go. You could also use the Velcro technique on a flatter dog bed (like the padded crate mats) if you prefer. My pup just sees them as stuffies, so it doesn’t work for us. Kurgo also makes a half hammock that takes up half a back seat that could work (didn’t for us because two big dogs). Also, Amazon has ‘car seats’ for large dogs (basically a box with a seatbelt and no lid) but it was difficult for us to fit two, and frankly, my dogs hated it. My vehicle has two captain chairs in the second row, so I needed something in the middle.
Great tips! I also use a non-slip mat under my dog’s bed. It really helps keep everything in place during the ride.
Have you thought about a seatbelt harness? It keeps them secure and might help them feel more comfortable. Plus, it’s safer in case of sudden stops.