[FrankJ]

We have run mecanum for the last two years including using the wheels to Auto Aim the frisbee bot. Running completely open loop we have had no control issues to make us want to pursue PID. We are using the jaguars in the absolute voltage mode. But we didn't have issues before.

My point being you likely have other issues to fix before going the feedback route. Mechanically all for wheel need to have firm contact with the ground and as equally weighted as practical. Without your bot will not go straight with all 4 wheels turning the same speed.

Although you might get a little from manufacturing tolerances, CIMs don't have a bias for one direction or the other & should turn the same spreed given the same load & voltage.