Bandit you know my theory on all of this...give me the plate
I prefer 4 umpires to a diamond...depending on situation of the weekend, either a 2 on, 2 off rotation, or a 1 on, 1 off rotation. First gives you two partners; Second gives you one partner all day.
It's hard to get a rotation that let's you switch diamonds unless you have more than 4 per field. Then you could get 2 on, 3 off, switching diamonds.
I prefer 2 on, 1 off with three umpires. With four I prefer 2 on, 2 off, unless it's really hot, then 1 on, 1 off.