Dear Paul,

I have made some tests, loading both images into Aladin. It seems to work OK.
As you can see on the attached screenshots (X-axis increasing to the right, Y-axis increasing to the top), Aladin's default behaviour when loading a FITS extension file is to create a dedicated folder and to put the different extensions under this folder.
(If needed, it is also possible to load only a given extension by specifying its extension index).

Let me know if you need any specific information related to Plastic.

Cheers,

Thomas