You're welcome, Ben. I apologize for the careless "catalog" just before the second semicolon. Of course it should have been "collection."
In thinking about your grid work, I thought the following about Apple's Aperture might interest you.
I used Aperture before switching to Lightroom. The one feature I miss most now is Aperture's light table capability, which worked just like a light box + slides in allowing (among other things) the thumbnails to be arrayed in any way one could wish. (I still miss other features of Aperture, but I don't want to go too far astray in this brief reply.)
In some of my Lightroom collections I now use "spacers" (as I call them), which are virtual copies of a 50% gray jpeg. Spacers allow me to separate groups of thumbnails (e.g. by color/BW, or by horizontal/square/vertical images) in sequences that I find easier to examine than completely contiguous ones. I find such spacers unnecessary in Aperture's light tables.
Those light tables are still useful, though. If the situation calls for it, I export small jpegs from Lightroom, add them to Aperture, and work with them in a new or existing Light Table.
Jeffrey