The cover fits great on the seat backs and can be snugged down as tight as you want. The bottoms are held in place by an elastic cord, it is not quite as strong as I would like, but it has been keeping it in place so far.
The larger bags on the seat backs do take out a lot of leg room for the rear seat. The bags that come with the cover aren't the easiest to remove and replace. I can remove the lower bags to give rear passengers more room, but it takes a while. I'm thinking about trying some different bags down there that are compatable with the plastic molle clips to speed things up. I can still fold my rear seat down with them in place though. The camelbacks I am going to be adding are going to be thin, so hopefully I will be able to leave them in place. The good thing I guess is that I don't have rear seat passengers that often.
The material is pretty thick, I'm not worried about tearing them.