Page template (XPGT) file

Bob Russell asked:

What about the .xpgt file? It is possible to deduce most of it, but more complete detail would be good. (like: reducing the top margin on the first page, and interaction of column min-widths and font-size…)

And how will its operation fit with future implementation of the OPS extra CSS properties: display:oeb-page-head; display:oeb-page-foot; and oeb-column-number:[integer]; ?

Better late than never – here are some details.