I had a fair amount of wheel to tire slippage on my Jeep, not completely surprising when running between 1 and 5 psi for the most part.
After getting tired of rebalancing the rears I took a sander and made a notch in a ridge on the sidewall by the valve stem, just like you did with a marker.
Let them slip up to 20-30 degrees and then moved the tires back into position. Eventually I tired of doing that, too, and simply swapped the rears side to side. Now I could go on more trails before having to do anything since the tires could move 40-60 degrees before needing attention.
Yes, I'm lazy. So what?