Readability Font Size

Readability is a web service that reformats text on a web page to make it more readable (it was the basis of Safari's Reader feature). It's expanded to do more things but I tend to use Instapaper for those features. Still Reader pops up in several apps that have embedded web browsers and it's very handy on mobile devices.

When Echofon stopped supporting their iOS devices I switched to Tweetbot. It's not cheap but it is well done and has a lot of features, most importantly sync between clients (which I use between my Mac, iPad and iPhone). It has an embedded browser which I use often because people (like me) tweet links to articles. There's a nice switch on the bottom of Tweetbot's built in browser that lets you switch between a web page view and a Readability view and in Readability at the top of the page you set the theme, color and font size. But here's my issue, I really wish there was a font size between these two: