Bill & Dave are dead on with my experience. They're a little more fusiform, and not nearly as prolific. I put in about 25-30 RES in my pond and have had no recruitment. Not sure if they all get eaten, or if the BG just push them out. I'd be (am) concerned if you have mixed sex RES with male only BG - I just don't know enough of the implications of the cross other than they're beautiful fish. But if no BG, I think Bill & Dave are dead on.