britax frontier tether strap fitting seat weird?

We just got 4 (argh!) new britax frontiers for our 2 cars b/c kids still need to be in harness but hit height limit for the convertibles we had. In one of our cars, the tether straps are being a little weird b/c of where the latch hooks are for seat placement and the way the seat back is shaped- the seat back is slightly curved on corner of the side close to the door (this is an SUV so the seats fold forward)... in our other (also SUV) car (car #1), the seat backs are very squared off on the corners so the tether strap went over the back just fine. Car #2 required a bit of shifting & finagling to get the tether to not lay on the rounded corner...we plan to keep an eye on it but I guess my question is, is this something that will be a problem regardless of which seat we buy (I don't get the impression we have too many options of seats anyway) b/c they will all have the tether straps in approximately the same place?

Also, similarly, our last seats were Britax but there was a tightening strap on BOTH side of the LATCH. On the Frontier, it is only one side and when I tightened it, it feels like the side w/ the tightening strap is so much tighter than the other...I sat in the seat, leaned toward the 'looser' side and had my husband pull w/ all his strength on the tightening strap but it still seems crooked somehow. I am probably overthinking the whole thing (MH thinks so considering how many ppl we know who just put their kids in regular boosters before the recommended weights, etc...)...

Anyone else run into these issues?

Thanks...