Nick,
I wanted you to try running your input file with everything the same except changing your feedback stimuli into something besides text files (i.e., using the # operator in the stim column). Even if the feedback messages are text in the stim cells (i.e. using the ~ operator), you can still give a unique font, size, and color to each message. Open the Styles file for your study and create however many individual styles you would like for your feedback messages. Then just reference the row number from the Styles file that you want to apply to the each text feedback by using <#> in the same stim cell as the feedback text. For example, you can type ~feedback 1 <1> in the stim cell to use style 1 to display the text "feedback1". This will trump whatever style you define in that row of your input file.