Not sure about re-marking your large mat--mine was not a self-healer and large, too. I'd tried using the Mr. Clean white sponges, the kitchen sponges with scrubbing on one side, regular "scrubbies" and finally decided it wasn't just a "need to clean" issue but I needed to smooth the cut marks. I would think it you do try to re-mark it, that you first want to get it super smooth so any lines will be even. Maybe after getting it super smooth you could use a very fine line sharpie to mark? What does everyone else think?