Whenever I’ve done a flattening run on anything, whether a spoilboard or work piece, there have been low ridges. I finally made a CBE tramming device out of dowel and length of stiff wire. It bounces, but is good enough for my purposes. I got the Y axis set very close, but the X axis isn’t really adjustable. Even so, today’s flattening passes on the fountain base have ridges that are barely noticeable to the finger. They show up visually, but that’s due to the wood fibres. Given that this is end grain, I’m satisfied. The base is now 105 mm thick with a ± variance of about ±0.05 mm in the Y axis and about ±0.2 mm in the X axis. That’s with the spoilboard as reference, which isn’t necessarily flat either.