I can’t get Gunny to get in the back of the P1 although he goes Ape chit when it fires up! He’s ben in the front a few times. Thea got into the P5 a few times but gets a little paranoid when we start to move! But he’s a hell of a co pilot in the truck!
I have the DUSTY DOG rear rack assy on our P5. Once I placed a think rubber mat to the floor our Basset boy Gus had no issues riding. He also wears a body harness and safety belt.
My Jagd Terrier love to go. 22 lbs so not an issue he lays on the seat with his head on my lap or sits up in the wind. As for jumping out he has been trained for hunting so he knows to stay put unless released to flush game so that’s not really an issue. He loves to run beside me or course across in front looking for grouse or rabbits. If you really need to keep them in place try a harness designed to clip to a seatbelt.