DPlot

I'm using standard letter, landscape, default margins (around 0.2) page. When I do NOT check "Specify plot size" under Extents, the graph fills the page. both on screen and when I print. If I check "Specify plot size", I can't seem to get over a 9" x 9" size. I understand it will limit the size to the available page and margins but I think I should be able to get around 10.5" for the width in landscape. It doesn't matter whether I change it to portrait or landscape, I can't go over 9" x 9". It fills the height nicely, but leaves a pretty big gap on the width. I'm wondering if I should be able to duplicate the size of the graph when I specify the size compared to when I don't and the program takes care of it. I want to get more width than it's allowing me on a landscape page.

It's the 9" height you're specifying on 8.5" tall paper (in landscape) that is causing the width to be reduced. If either the width or height won't fit, then both are scaled down by the same factor so that everything stays proportional.