I thought I'd seen the answer to this question in a previous post, but now I can't find it again.
On the diameters of the baffle, should the 120 degree part always be 1-1/4" larger than the inner circle or should that be larger for a larger barrel with 4" hose?
The drop slot is sized to the media you're separating. For hardwoods, 1-1/8" to 1-1/4" works fine. For softwoods, 1-1/2" is probably better.