There's a story arc I want to cover that I set out at the start, and the structure of the chapters sort of follow milestones in that arc, but some of it is definitely seat of the pants. For instance, I'd intended to some of the events from chapter 4 in chapter 3, but when laying out the events on calendar, it turned out it was too many to fit in a single week, so they shuffled over and folded into chapter 4 events. Another example is the whole thing with the 3 office ladies, which sort of happens as I go along.
As to how where we stand compared to the original plan; well, with chapter 4 we'll have covered a decent portion the original outline already, and if I were to follow that original roadmap, we'd be about 2/3rds-ish to completion. But along the way, there's also been quite a few ideas that presented themselves, and, if the audience is willing, we might as well visit a bunch of those and take the scenic route, so to say, provided it doesn't water the whole experience down and allows for the audience to finally taste some of that dangling fruit, mind you. But those aren't fully formed ideas just yet, and developing those ideas further will have to wait until after chapter 4 is out.