Those results look very good. When I've tried this with normal colour C41, I've not had the best of results, which I've put down to the orange mask (which C41 colour tends to have) and the fact that C41 tends to be a bit lighter in silver than "Proper" B&W, as its just there for light capture, and something for the dye clouds to form around. It certainly isn't in the final negative.
So Rodinal 1:100 on stand. Can I ask what temperature, and for how long?
As I might give this a quick whirl on some cheap Kodak Colorplus I bought a load of