Yes, have the seat in the middle right now in fact. Wife sits on one side, daughter of the other. Gives the both more room and grandson can see the road better. (He's become quite a backseat driver).
I use the anchors in the seats like you described, but not all car seats can be fastened this way.
If your in a hurry you can just use the center seatbelt, to strap the car seat down. Seat wiggles a little more, but not enough to come loose. When using seatbelt fastening, I will "put a knee" in the carseat to push it down harder when tightening belts. (Holds car seat more securely).
I also always use the "over the top" strap. Minor problem with the center seat is the center headrest doesn't raise up (allowing the strap to go between the headrest and seat like the side seats). So I just run the strap over the headrest to the fastener in on the back of the seat. Feel that the "over the seat" strap is important to use.
BTW, seventies is the new middle age. Ha!
Edited by enigma-2, 03 May 2017 - 11:59 AM.