Purpose of extra umpires? (5&6)

[DG]

Can't say I have ever seen a book with 6 man mechanics in it, and the only game I have ever worked with 6 men I was behind the plate. The pre-game was interesting, as we went through 4 man, and then I looked at the field guys and told them "I don't know what to say, other than get the trap calls in LF and RF and Fair/Foul on any balls near you, and enjoy the game".

But, I would think a LFU could call fair/foul better on a ball that lands just in front of him than the 3BU who is turning around and some distance from the ball landing.

Come to think of it, I was at 1B for another 6 man game and I don't think the RFU had a call to make throughout the game.