We initially purchased the Triad CSX with their standard seat with the back. My husband found it uncomfortable for long rides, so Jeff stepped in again with this recommendation. Sure to become a standard line, Jeff is from Tri Electric Scooters, one of the great authorized distributors of Triad products. Jeff and Missy, who run Tri Electric Scooters, are from Georgia. If you are down south, GO visit them!
One of the bonuses of this seat is that it still has a back, but the back isn't as long as the standard one that comes with the scooter. If you have a tight space to get it into, then it might fit with the lower back without having to take the seat off. As of Septemeber 2017, my husband still has the Subaru Crosstrek, and he still has to take the seat off to get it into his car.
We are still on the search for the ultimate seat though. So if you have recommendations, please post your comments below!