any reason to avoid px measurements in epub?

[Turtle91]

Originally Posted by JSWolf

So how would you get a border to be the same width on a Sony Reader and a Kobo Clara HD?

You are missing the point. I don't care how you would do it. I wouldn't want to even concern myself with trying. A 1px border is a 1px border regardless of the resolution of the device - the size of the font within that border doesn't really matter - the border still fits the cell regardless of the size of the cell needed to accommodate the font within.

IF someone cared about that kind of detail, they are welcome to try and figure it out. It is not something that an automated software conversion would/could get right. An automated conversion of a PG book certainly doesn't need to concern itself with stylistic minutia, so the OP certainly doesn't need to concern themselves with your question.