I just said in conversation:
J’ai jamais été un gros dormeur de base, plutôt du genre couche-tôt, lève-tôt, depuis je ne sais combien d'années.
Short sleepers are those supposedly genetically wired to thrive on significantly less sleep than others without showing typical symptoms of not getting enough sleep.
I meant the phrasing "pas un gros/grand dormeur" to mean "un petit dormeur" in a positive sense. I get the feeling, though, that "pas un gros/grand dormeur" may well sound as if I've been suffering from chronic insomnia instead.