I'm not sure I can recall ever seeing any firm guidance and I've run several part 23 and smaller spin programmes.
I'm on the wrong continent to check my copy, but I wonder if there's anything in Darrol Stinton's "Flying Qualities and Flight Testing of the Aeroplane" ? DS did a lot of this sort of work over a lot of years, and that book contained much of his distilled wisdom. The other place worth looking would be FAA AC23-8.
G