I'm sure you're right Glenn. I've had a look at the other pics of her, posted below, and there doesn't seem to be any Neutral Gray. However, in the stern view, the extreme underside, from the radiator exit duct aft, looks like it might be NMF, with the green finishing as a wrap around, part way around the underside of the fuselage.
The description states that it was 'Dark Green' (possibly ex-RAF paint stocks? Pretty common at the time) on the upper surfaces, fin and upper surfaces of the tailplane, with no mention of the green extending all the way underneath.
I'll admit, until now, looking again at the photos, I always assumed the green wrapped around completely.
Either way, the decision is yours mate!