Do you want the two layouts displayed in two windows like you get with Manage Layouts?
If so, you can do this manually by selecting New Window from the window menu and then navigating in the new window to the desired layout.
A script can do this with the New Window scritp step followed by a go To layout step.
Well, why didn't I think of that?!? Thanks much!
I guess I assumed that the "New Window" command would be in the File menu, as it is in most apps - didn't even think to look at the Window menu. My bad.