I know this is a pain of a workaround but the easiest way to change the font in Reading View is to right-click on the page, click 'Inspect Element', find the font to change and type in a new value. If you know a little bit about web coding then this shouldn't be a problem.
The painful part of it is that you have to change it every time you reload that page. It doesn't save your changes once the page closes. So if it's something that you can leave open, this is a doable workaround. If it's something you have to keep coming back to, then it'll take an extra 5 seconds to change the font each time.
Hope that helps a bit.
11-19-2015 12:00 PM