Yeah it should be fine. I routinely bounce at least that much if not more with the camera tilted on its side going off of a wall. Even if it was a stretch I'd still get the 400 for a D40 anyways, because the SB-600/800 flashes handle so ridiculously poorly on the 40. The camera becomes very top-heavy and imbalanced and the feel is very unnatural and awkward. For any prolonged shooting, it'll suck. The SB-400 is great and nearly weightless though, so no problem.