Try wire ties as stops for the car top carrier mounts. See if you can use bike tool cable tightener to tighten wire ties.

need extension on yakima rack and roll for long yak

https://paddling.com/reviews/product/yakima-rack-and-roll-trailer/

I like this one:

https://www.sportsrig.com/shop/microtrailer/sportsrig-adventure-trailer.php

person using unistrut for bars had a failure. looks like too much torque on it and it twisted the fittings.

https://www.youtube.com/watch?v=zj8V61hCN18

forester is 70.7 inches wide