I picked up https://www.daz3d.com/dforce-ebenezer-scrooge-nightdress-outfit-for-genesis-8-and-genesis-81-males tonight as it was on sale.

Usually, I've no problem with mixing things up, but this item really exhibited an issue I've seen over the years, but never understood what what going on or how to correct it.

I put the nightshirt on a G9 figure using the Auto-Fit scripts and select the prompts for the G8 Male and OKed them.

I then put it on a G8 figure and no auto-fit prompts of course.

The results are obvious. So is there a means to go "Out of Figure" and correct in these cases?

Once you pose the character and apply dForce simulations there should not be a problem. Or at least that has been my experience.

The 1st image is immediately after it goes through the fitting stage. Fine until then.  Simming doesn't help. Fortunately, I've lots of G8 figures. But I've some ideas to try for non G8.

When you AutoFit DS tries to adjust the sahpe of the fitted item to match the shape of the new figure, but the less closely the item follows the shape of the original figure the more likely it is to get distorted - and in this case the garment hangs straight down, so the converion process adds all sorts of bumps. It might be simpler not to fit it at all, just pose your figure to fit inside the zeroed garment, memorise the pose (Edit>Figure>Memorise>Memorise Figure Pose) and run the simulation like that. Still, as GGreen says, even with the bumps running the simulation will probably laegely smooth it out.

I'll give that a try certainly. Sort of what I had in mind.