I tried the "Large Code Font" option, which does increase the font size, but I prefer the smaller code font.

On a side note, all "Large Code Font" does is suppress a <font size="-1"> tag around the code block. If you prefer CSS, the text in large code blocks can be matched with tt.codetext and inline code text can be matched with tt.inlinecode. Since the <tt> tag overrides the font-family, matching the outer p.code is not useful here.

Bizarrely, if you want to use CSS to customize this, you will need to check "Large Code Font" — otherwise the <font> tags will override your careful efforts.