Originally Posted by dwanthny
1st, Sigil is a great tool and has many fine features that help fine tune any epub. That said there was a new feature added.
What version of calibre are you using? As of 0.7.51 those margins should be zeroed out automatically. I tested this with a epub book that had left and right margins and it worked fine in eliminating the original margins.
I upgrade Calibre each time I'm prompted. It's at 0.7.52 right now. When I highlight a book I've never modified and go to page setup, left, right, top and bottom margins are all set to 5pt.