Hi denbutler,

re:
> Try this experiment:
>
> 1) draw a solid box on one layer

Ok this is what I drew:



> 2) draw a sphere intersecting the box on a second layer

I made this:


> 3) boolean difference the two - not keeping objects

Ok, that makes this result, it's a solid with some of it's faces assigned to different styles:


> 4) you should now have a subtracted solid, but appear to have two polysurfaces, one on each layer

Incorrect, I've got a single solid which has some of its faces on one style and some of its faces assigned to a different style.

For example if you click on it you should see it select as one object because it is one object:




> 5) save file and reopen
> 6) now you have the subtracted solid, on its original layer

I saved to a 3DM file and reopened and got this:



Did you save and reload to a different file format than 3DM ?


So it sounds like you don't like the feature in MoI where it allows different faces of a single solid to belong
to different styles. If you like you can disable the generation of multi-style solids like that by a
setting in moi.ini:

[Styles]
DisableSubObjectStyles=y

- Michael