Variable-pitch and fixed-pitch with the same font-size?

Question

I've learned here that I can customize my variable-pitch font. For org-mode, I'm using that customization together with the following snippet to get a mix of variable and fixed-pitch fonts:

(add-hook 'org-mode-hook
            '(lambda ()
               (variable-pitch-mode 1)
               (mapc
                (lambda (face)
                  (set-face-attribute face nil :inherit 'fixed-pitch))
                (list 'org-code
                      'org-link 
                      'org-block
                      'org-table
                      'org-block-begin-line
                      'org-block-end-line
                      'org-meta-line
                      'org-document-info-keyword))))

Everything except for normal text is displayed in fixed-pitch, which is displayed with variable-pitch. The problem with my solution is that the font-size for both fonts is different and the variable-pitch looks really small and hard to read. How can I adapt my solution so that both fonts have the same size?

(I also have the feeling that my solution is not ideal because I get buffer fontification problems every now and then in SRC blocks when opening files..)

Example image:

Answer 1

This may or may not be what you are asking for, but if you set the :height property (i.e. font size) on default to some integral size, then you set the :height property on variable-pitch to a fractional value and it will be interpreted as a scaling factor applied on the parent face.