Very interesting. I was sort of right, that there was a mansion at the point where the Yimaleti's come down into the Istyuli Plains, but not right in it being Siöl. I never thought of to place Nihrimsul, so defintely an oversight on my part.
Comparing the map from Som and this one, it seems that where Kellhus meets Moe near Kyudea was indeed not a high mansion, but rather might have actually been just a bathhouse/temple adjunct to Illiseru, as I think we had speculated it might be. (Illiseru has never been named in the books, that I could find).
Interesting also that one of the "unnamed Mansions" was so close to Cil-Aujas and at first, I thought about the source for Chanv. It is too far West, because it is rumored to come from the headwaters of the River Sayut. However, the idea that it was an adjunct mansion they are mining for Chanv is definitely possible.
Interesting stuff for sure.