Superscript tags with PDF Writer

I was wondering if you could answer a question for me. I’m using PDF writer to create a PDF document Some of the text output requires a superscript to denote a footnote. I was able to insert tags to surround the footnote number. I created the following tag code to change the font. The code works in that the number is raised by 5 points. The problem is that I can’t change the font size. I’ve tried several different approaches such as changes to the :height variable, :font_size => 8 and pdf.font_size = 8. Any thoughts how I can change the font size? Thanks

class TagSuperScript 

  class << self 

    attr_accessor :font_size 

    def [](pdf, info)
      case info[:status]
      when :start, :start_line 
      info[:cbid] = {
          :x       => info[:x],
          :y       => info[:y]+5,
          :height  => info[:height],         
          :descender => info[:descender],
          :font_size => 8
       }

      when :end, :end_line
      end

    end
  end
end

PDF::Writer::TAGS[:pair]["sups"] = TagSuperScript