Reading FreeType documentation, it seems I really should have read these pages before I reimplemented Typograffiti text rendering! It warns me about issues I'm having as I test just a tiny bit more!
https://freetype.org/freetype2/docs/glyphs/glyphs-2.html
O.K., get font sizes & baselines working tomorrow... I've learnt the necessary jargon to do so: ppem, ascent, & descent!
New release of Typograffiti coming soon, which should look much more legible!