I don't think I do anything unusual...(and, yes, I use Inkscape). I create a temporary layer under everything and put a box on it that just covers the area I want to export. Then I make that layer invisible while I've got the box selected, so that I have the correct area selected but I won't export the box as well. I look at the size of the box in pixels (at the top of the page), and when I get to the export options, I make sure the exported picture's size is the same as the box, so that I don't accidentally resize my comic while I export. And that's it. Did that cover what you wanted to know? I'm not quite sure what you're asking