@GeoffR -
I only use kepub's so don't know what would happen with epub's.
And because I don't want to "force" my reader to something, I don't use any of those "forcing" patches.
as wrote above, I meant the "my 10/24 line spacing value" patches at the beginning of the libnickel.so.
I will test it tomorrow with another kepub-book first and report here. (also will have a look then wich patches are enabled, but now i'm away from my pc)