Regarding the size of DV windows, you'd be surprised. I did "dunker" training on helicopters years ago. The cabin window was pretty small, and with a waistcoat life-raft strapped on the average pilot was of greater size than the window. Having been rolled and pitched underwater, everyone managed to get out of the "too small" window. I agree with BOAC though; the DV window is a "secondary" escape. It's a long drop if you get it wrong.