[gaphic2]

@ Charleski: No, no cutoffs at all in ADE. The space varies.
CSS is plain vanilla.

But I think I've cracked it. I's caused by long paragraphs! I've combined and split a few paragraphs and that has an immediate effect.

There has to be something in the rendering software that tells the reader to break the paragraph if it is longer than X (screens?). This would account for the different behavior between the two readers.

I'll do some more testing to find out if I can come up with a number of characters. I've attached a test epub with placeholder text, a couple of pages, all in one paragraph. On both my readers, page breaks seem random. Surely there must be some logic behind the breaks?