I am switching this to a separate thread as there seems to be a large interest in it.
I have run large a few very large 15mm ACW games. I have discovered a few "must haves" that have made them successful. Many of you have already mentioned a few of them.
I will write down some of my observations. And the game would be easier as a club game, since there are so many of you that own 15mm armies already.
Note _ I have played all 3 versions of FnF and strongly recommend FnF 1st edition brigade rules. FnF Brigade 2nd edition are my favorite, but mostly for some rules clean up and adding the firing tables from the regimental set. For a large game though, FnFB is deadlier, so you reach conclusions faster.