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My experience has been mostly surface prep so far, it comes nice and flat but is a hard stone.

Yes, and a few of those are relatively local to you. :gl:
Enjoy your Roszutec, I have one but haven't used it much yet. I've been playing with a Dalmore Blue and a Quartzite hone.;)

Henk Bos has some information on the Roszutec stones.

https://bosq.home.xs4all.nl/info%2020m/grinding_and_honing_part_3.pdf

It can be found on page 111.