My car does a pretty good job of being a dual duty commuter and HPDE car, and the only real downside for me is getting an alignment that balances tire wear for highway commuting and track use. I just finished an alignment for the off season, and I always find adjusting the rear camber to be frustrating with so much crosstalk between camber, toe, and thrust angle adjustments. It's a lot of getting up and down and awkward reaches through the suspension when using alignment stands rather than a vehicle rack and laser alignment system. In addition, I also couldn't dial out as much camber as I'd like and -2.0* was as flat as I could get the tire in the rear. I'd probably get more frequent use out of my alignment stands if adjusting rear camber was less work.

To make for easier adjustments and increase the usable camber adjustment range, I am considering getting a set of AWR adjustable RUCAs. They're basically a stock part modified to use an additional eccentric bolt at the top of the upright.

My question is - Do the adjustable rear upper control arms do a good job of isolating camber adjustments and not affecting toe? Are there significant downsides to adding an adjustment here that I'm not seeing?