One reason people are asking to see the problem is related to the comments that Japanese plane soles are not flat: certain parts of the sole should be in line, while other parts matter less or not at all. The toe, the heel, and the part of the sole just in front of the blade should be in a plane. Since your 12" rule is not long enough to span the important parts, it is possible that your plane is set up perfectly now, and that grinding out the hump may make you need to grind a lot more to get the plane to work well again.