HI Sunny,
As long as they ALL point to the same location when ya really really need them, then I guess 1 would one do.....or two for luck,.......
In my former occupation I have seen and had experiences with 'fixed ELT's' which were not always 'nice'.
Hence I prefer the personal 410G style, which I can have control over, to supplement the mandatory fixed one, which sometimes 'doesn't'.....
Rotsa Ruck
