[MD Longhorn]

Honestly - both of these viewpoints can be right. Given that ASA didn't bother to define "projected sub" - going back and forth is rather worthless.

As long as we are self-consistent during a game, either way should not have problems.

Method A - To my mind, a person doesn't enter the game until she actually begins to participate and the person she's replacing is no longer participating. On defense, this is easy and we don't seem to have any disagreement. On offense, TO ME, that means - when they are about to come to bat. If this is your viewpoint, and you A) don't write anything down until it becomes official and B) notify the opposing coach and the scorekeeper of the change at this moment (and not earlier), you will not run into problems.

Method B - Conversely - if you go with Dave's way (which is also Irish's way from a previous thread), and accept any changes to the batting lineup in advance of the inning started, then as long as you A) write them ALL down when the coach gives them to you, B) inform the opposing coach and scorekeeper of ALL the changes when you write them down ... then again, you will not run into any problems. (Probably should inform the coach making the changes that they are official as of that moment too, just in case the below cases happen)

The only real difference lies in the two cases mentioned above:
1) Coach says Suzie is coming in for Sally to bat, but Sally's AB never comes - with method A, Suzie has still not entered the game, and Sally has not left... with method B, Suzie's already in the game, and Sally is not.
2) Coach says Suzie is coming in for Sally (batting later than Beth), but Beth gets injured during her at bat and coach now wants to put in Suzie for Beth... method A - no problem, coach; method B - No coach, Suzie's already in the game.

I think you run into no coaching issues in either of those cases with Method A - and you could with Method B. But again, as long as we are self-consistent and communicating with the coaches, we can justify (by rule) either method.