Well, being a rookie team, we did not put a lot of work into ours
We pained a wheel black, and then used white-out to put on the white marks... Eventually we went to 1/2 white 1/2 black. It was quite precise, at least our autonomous mode was quite consistent. We only counted wheel rotations, and I used a correction for slower speeds - I skipped some loop iterations to avoid reading the same line twice. Turned out I didnt need it
Next year we'll definitely have an extra counter circuit.