Julien, > I am interested in seeing the interface and implementation, given that I > wrote something similar (but probably less thorough since mine is > essentially wrapping NFSS/latex2e) Here is the module source: https://github.com/tail-reversion/soranus/blob/master/fontsize.tex There /was/ user documentation for this module, but a mistake on my part means that said documentation has ``disappeared''. Hopefully, the source is clear enough. Please excuse the mess of a repository. And I plan eventually to switch over to dtx files, but presently I find it easier not to fiddle with docstrip. I like the idea of making font sizes relative to the main document size. I had actually experimented with exposing the normal size as a public variable for use in instance definitions, but I found the dimension scaling to be of unsatisfactory precision. However, I just learned that the l3kernel provides floats of higher-precision than TeX dimensions, so perhaps that could be a solution. -Kelly