Scope of smart albums under C1Pro Fuji 12

I'm deep in the process of converting from Aperture to C1Pro (still version 12 as it all started 2 years ago!). I'm trying to use the Smart Albums feature to re-create as close as I can the situation in Aperture where I could click on any element in that structure and "see" (and filter on) all the images within that structure. The structure I have at the moment in User Collections is to have a Group per camera, within each of those a Group per year, within each of those a Project per film and inside it a single album for the images of that film. AFAIK you can't "see" any images at the Group level, you have to select a Project or an Album.

Anyway, I created a Smart Album under the "Pentax New" Group, called "Pentax 4 star", and it does indeed show me only the 4 star Pentax images. But when I try the exact same approach under the "Olympus New" Group, then the "Olympus 4 star" Group shows all the 4 star images in the Catalogue!

Can anyone suggest where I've gone wrong?

I tried to insert a Project ("Oly temp") under Olympus New and move the Groups under that, but it wouldn't let me. It appears I can create a new Group under Oly temp, but then I still can't move either a Group or a Project under that. The only thing that will go in the Group under Oly temp AFAICS is an album (or albums).

I think I've got myself quite confused. Is there a way to simplify the structure?