Speed/Od-ometer: Has anyone bothered to recalibrate?

[arctictraveller]

Speedos are calibrated to the original tire size when new. My 32 in tires introduced an error that was corrected when I re-geared to 410's. At one time I thought Chris at U-Joint offered a black box of some sort that allowed you to re-calibrate, you might check his website. My scan gauge also has a speedo built in that I seem to remember can be calibrated.