The only interference from the umbrella-style rod, Sam, is to help further soften and diffuse the light (yep, that's what I'm saying). In fact, in beauty dishes they put in a plate to achieve a similar softening effect by scattering the light rays further. That octabox also has 2 levels of diffusion - the outer white cover and an inner (removable) white scrim. All-in-all they make a great modifier, especially if you are opting for just the one strobe. And no, they don't cast any shadow.