OK – figured it out, just needed to set a width for the callout inside the 2/3 width column. The callout is full-width by default.
Here is a page with a gallery at the top: http://mussermodels.com/gallery/hms-druid/
All of the individual ship pages (all the children of the “Gallery of Ships” parent page) are the same format, with a gallery at the top of the page – and all are displaying the same way.
http://mussermodels.com/
At the moment I have the thumbnail size set to “auto.”
Thanks!