Sorry I can't help with measurements, too many variables, your weight, extension out of the frame (lever arm), etc. I did one fluted Laprade from the early '80s, the gouges where localized at the rear of the post a few inches above min insertion. I used a 1 1/2" emory cloth rolls like I was shinning the toe of a shoe, only at the area of the gouges with the post secure in a vice. After finer grit it is impossible to see any change in the post, very smooth transitions. Did not need to take much off and was not worried as the material resisting bending on the sides of the post rather than the front and rear are more important. High tech posts like the Thomson Elite have elliptical bores with thinner sections in the front and rear of the seat posts to save weight.