You'd be mistaken. I'm not saying its never been done, just you'd be breaking the rules. I don't know of anyone that goes closer than 1/2. There's still rumours of guys crawling up legs and that sort of nonsense but I've never seen it done.
Speaking of twins vs. singles, I've had a 47 and a 206 quit on me, had another 206 that I had to get to the ground NOW, had a 222 roll one back to idle, had to shut down one can on a 76, and had the aforementioned failure on a 61 last year. I'll take a twin please! Of course, the water is a little warmer in the GOM compared to the North Atlantic.