It's necessary to move up to a 20” planer. I am a part-time wood worker and I work with old New Orleans barge boards. The majority of them are 16 to 20”s wide. A few are 26 to 30”s wide but the few times I used these width, I'll work them by hand. I am interested in spiral cutterheads. If a nails get by, only damage is why you called a few inserts are damage. My concern is how will a spiral cutterhead work with old paint. The normal process is to de-nail, scrape, wire brush and sand (a lot of sanding). Then usually a light planning. I am trying to do away with the sanding and more planning. Thanks Wither