I'm wondering if the only answer would be to solve the problem of a phenolic fingerboard shrinking is using WD-40 on it to keep it moisturize in some way (not really the word I was looking for but you got the idea).
I don't think it's really treating the fingerboard the way oil does with wood. It's just for cleaning. I think the phenowood is pretty much impregnable...




That gets expensive with flats.