My pop up was a single axel,my TT is a double. I like the stability of the double much better , driving with it and parked. The duel axel will feel less shakey when parked and set up. Agreed with backing up, the single axel will respond so much faster, it takes time to get used to. Addtionally, if you forget to drop the rear stabilizers, you can tip a single axel. My duel axel is a smaller camper, and I have no problems getting on any site. Its almost the same size closed up or open as the pop up was. So not all are huge behemoths that you need special sites for.
