What is the overiding advantage of being in "A" vs "B" when no one is on. I am thinking that 85% of the time the field ump is rolling out to "B" and making routine calls at 1st or 2nd anyhow.

The A position is the absolute best position to determine if a pitch is legal, or not. Unless we are prepared to ignore all of the footwork, being on the lines is absolutely the best location to determine if both feet are on the pitchers plate, as well as crows hops and leaps. It seems to me that starting in the B position is a statement that we DO plan to minimize illegal pitch calls.

It is a much rarer circumstance, but if you are going out on a fly ball to right, you can't work the fair/foul line from the B position, either.

The reason this will not change is the advantage an umpire has in the A on calling seeing the IP that you cannot see from B or C

I seem to remember talk over the last few years to move the BU to the B position all the time in two-man slowpitch mechanics.

I seem to remember Billy P being an advocate of this mechanic.

Mike - do you have any other information on this?

I believe "A" was dropped in slow pitch

He was. He used it when we partnered and he had the bases, and suggested I give it a try.

It does have benefits for being in position for calls on the bases.

It does have disadvantages for the IP. Hence, I don't use it.

It works well in SP. The only difference between the two disciplines is watching the pitcher. Relatively not worth talking about in SP, but a serious part of the BU's duties in FP.

BTW, Billy P also advocated the BU stay outside on balls to LF. That's all fine and dandy until the OF drops the ball when throwing it and you are so far out of position for a call at 3B, it's not worth it.

Staying out on a ball to left field is a great mechanic when used properly. Stay out on a routine fly or single that may be stretched into a double. You have the ball, runner and fielder in front of you for a tag play at second. I only use this with no runners on; If something unusual happens the plate umpire can easily come up to third.

With a routine double or fly ball to the gap, you still come to the infield and be ready for the runner advancing to third. I like it, but there needs to be a little modification and pregame discussion with the plate umpire about the runner going to third if the ball eludes a fielder.