I'm interested to see what your opinion is (OP) after trying it out. I've not had good luck on my stomach in the RR. It seems to have more of a give in the butt area than does the JRB-BM. Enough of a dip that I seem to get a little hyperextension. I've found this to be true with a fully inflated pad as well.
That said, I sleep plenty well in it. I think I only tried to get on my stomach because its what I'm so used to at home, not because I really needed to in the hammock.