As you may have noticed that the discussion at hand is dealing with extreme and rare cases. The people involved are all very experienced RCers who take all the normal precautions. All these diodes and fuses etc are for those 1% problems that arise and not for the standard run of the mill problems we normally encounter. When very expensive aircraft are involved, I think Leo is trying to cover as many bases as he can. I fly single Nicad system myself and replace the batteries every couple of years. I have never had a problem, but I'm a big KISS person so in my book less is more. I also don't fly multi thousand dollar airplanes either.