I am finding that while lapping, especially the Naniwa SS 8k (yellow), the stone does not seem to stay flat after use. I can mark it up, lap the pencil completely off, hone one razor, mark and lap again, and the effect of the lapping plate on the stone is not as expected. It also seems to take much longer on the 8k than the SS 5k and 12k. The Chosera 1k is not having the same issue.

I have been told that the synthetic stones can flex if not mounted/lapped on a completely flat surface, like granite, especially the SS stones as they are quite thin. Given this, the stone could be lapped while deformed from flat in the hand, leaving it not perfectly flat in the stone holder.

Has anyone else experienced this?

Has anyone mounted these to a flat/rigid surface like a granite tile? If so, what adhesive should be used?