[AnEnglishmanInNorway]

This started as an idea to deal with the repositioning of content on pages after the point at which a single page was added. Double pages are often artistically laid out as a unit, perhaps being more compact near the center margins, and more sparse at the outer edges. Add just one page, and this asymmetry is suddenly the wrong way round from that page onwards dense at the outer margins and sparse at the center. But I couldn't find a sensible algorithm to correctly rebalance that, and have deleted those trials.
The final result was a small utility which would center the bounding box of the contents of a page on the page, for selected pages. This is probably the best solution in any event, when we are creating a single page width pdf, avoiding a slight jumping of the balance of a page from left to right and back as you leaf through the document. Go out of the album editor, apply the center content utility to the mcf, and return to the editor to check the result and continue editing.