What I did is take the same workaround that a few others have. I don't know of a real good solution to integrate Coppermine visually, so I just made it look like the rest of the site.
I don't need user integration, so Coppermine is running standalone in a subdirectory. I simply changed its template by copying the important div's and CSS styles from Versatility II. That's what I meant with "stripped down", mimicking the looks of the main site by using some of its style definitions.
The drop-down menus are a problem. Since the main site will get more and more content, the menus will grow, and there is no simple way to keep an off-site copy of the menus up to date. I wold have had to add each menu item manually on the Coppermine install. So I decided not to do it at all but just have two menu items: one for the gallery start page, and the other one for going back to the main site. Not very elegant but it works as an interim solution for me.
Kind regards,
Zorro