Do you find that the bars are showing signs of being canted side to side that quickly " every 4 sharpenings?"
I also think of a trick I see guitar Luthiers use when checking for high frets and using straight sanding blocks to level high frets. I watched the demo's of bar truing for square rails and feel this guitar trick would be good to adopt as well. The Luthiers will take a Sharpie and mark the tops of the frets and as the sander passes over all the frets, the high ones will lose the Sharpie mark but the low ones will stay colored until all the high ones are lowered evenly. I can see myself using this on the bar rails and combine it with square checking with a carpenter's/ machinist square and sight down the entire bar.
