Also speaking of what I said about finding a desired SID, I could be wrong on this, but is the cutoff point (the point where SID is determined) the moment the screen turns black (after the player character image disappears)? I tried it, thought for sure I got the desired SID, encountered a Zigzagoon after retrieving the starter (at a certain frame), but it wasn't shiny (if it was, then I did it right). If that's not the correct point, then I'm still curious where the actual cutoff point is.
I've had quite a number of unsuccessful attempts now, so yeah.