And for the sake of completeness, I've also found spammimic http://spammimic.com/. There is a paper at: http://www.nic.funet.fi/pub/crypt/old/mimic/mimic.text

Vast markup language, Knuth's TeX, and more so Metafont, provides a huge space as 'carrier medium. For eample, kerning alone, using float/real values far beyond what a human eys can tell. Off the top of my head, ... no, I won't try to guesstimate the dimensions of this carrier medium giant play room single-handedly. It gets messy describing what appears odd and questionable. The foo.tex could potentially grow arbitrarily large.

No compression here, as html, the Tex source is larger than what we view.

Another carrier medium layer to consider:

Per longish decimal variables, eg, in \kern, there is also

arithmetic encoding(See wikipedia)

which maps any size foo onto a real value in (0,1). I think there is a proprietary/patent troll war on this.

Choose natural language with many digits/decimals, tables of sports statistics. A stego, in C I think, around 15 yrs ago, created a familiar baseball sports page with decimal tables. ...etc