Hi Jeff,

> I also tried repairing the body after doing the boolean diff, but
> that experience didn't go well.

That was probably the same issue - the thing that looked like a hole was not quite exactly a regular open hole but actually a surface with a messed up trimming boundary. That needs to be removed so you really have a hole there that can then be patched up.

It's a bit of a tricky operation to select a messed up face like that since it doesn't have any of the regular shaded display to it to click on (that's a side effect of having a messed up trimming boundary - messed up trimming means messed up display meshing will happen as well) - instead you have to do a strategic window select around it to select it and then delete it.

- Michael