Dangerous idea. The listing I've seen for a FOUR engined, uprated Lancaster was something like 340+ MPH with no bombs. However, limiting that to two Vultures and no defensive armament, even at night seems to be a dangerous proposition. The Mossie got away with it because it was very fast, maneuverable, and had light-bomber style targets. I don't know that un-escorted and unarmed heavy style bombers could do the same thing.