Not all ePubs have an Adobe XPGT stylesheet, and the ones that do often use it mainly to set the page margins. Unfortunately those margins are added to the page margins set via @page in the CSS stylesheet, and cannot be overidden by the `ePub fixed/ajustable top/bottom margins` patch. This patch should cause any Adobe XPGT stylesheet in the book to be ignored, but for the book's CSS stylesheet still to be used as normal. (You might prefer to remove the margins from the book's XPGT stylesheet before sideloading, instead of using this patch. Calibre's Modify ePub plugin has a useful option for doing this.)