I’m surprised by this as 1.5 thou is probably less than the amount steel moves due to the temperature difference between winter and summer. If I made sure my planes were always flatter than that, I’d have much less time for planing, if I ever got to that level of accuracy to start with.I purchased a LN 62 to do testing and write an article a couple of months ago. It was almost intolerable to smooth flat wood as it was out exactly at spec concave (1.5 thousandths) to my starrett edge and feelers. The first several passes for everything was just to clip the ends off of the wood before finally being able to smooth. I flattened it and now it works well.