The seat has to be firm, and the belt needs to be "as tight as possible" in US and Swedish seats, right? When I am installing it I am really using my strength and I am a power lifter, so I know that I am not only stronger than moms here , but probably than most of their husbands. I am not saying this to brag or anything, I am just wondering if it is possible to overdo it, by maybe streching the harness or the tether straps, or is human strength simply not enough to make any damage to them even if you had Ronnie Coleman install your carseats for you?