The thing that has been more difficult has been the increased output expectations.
Yes. That and increased executive function demand.
I also second the recommendation to do as little as you must at once.
I personally tend to think it's a very bad idea to actually "skip" more than one grade level if you're talking about undifferentiated curriculum and expectations. That is, with chronologically normative peers, the developmental expectations increase fairly smoothly from one grade level to the next...
and are developmentally aimed at kids who are neurotypical in development. This means that you are pushing the boundaries with every year of "gap" between placement and chronological age.
So yes, baby-steps into the desired/appropriate placement always seem like a wiser strategy to me.
That way you know when you reach the limit of what is wise before you go past it. KWIM?
I never want my DD to feel that an acceleration is a "failure" because she, being a perfectionistic kid, would see that as a personal failing-- a catastrophic one.