Does anyone know how to fix Chrome on the
Nexus 7. So that it displays forum posts at a consistent size. This seems to be worse when I'm using Chrome

In the Chrome settings under 'accessibility' do you have the text scaling slider turned above 100%? Try changing it to 100%. Chrome is becoming quite bothersome lately. I've even started using Dolphin on my 10 inch tablet, the last update in Chrome made fonts too small and nothing makes it bigger. That accessibility setting is useless.

Easiest way is to use the Ds mobile skin. Select it from the drop down, right at the bottom of the page.