We just bought a Britax and the instructions are weird. Do you use the upper tether to install your RF convertible car seat? It doesn't look functional to use the one on the back headrest and we don't have one under the front seat. Help! Do you just use the bottom anchors??
SQUIRREL!!!

Re: Tethering a RF conv car seat?
hmmm idk then. we don't use it right now (RF). sorry i'm not more help.
We use it tethered rear-facing
This site might give you some idea
https://www.angelfire.com/wa3/isakswings/ratetherrf.html