An update...
Went by my LHS and picked up a bottle of XF-80 Royal Light Gray and did some muddling with white, red and light green. Also tried the XF-19 + White that the chart Phil_H linked indicated. The winner, at least in my eyes, is the tinted XF-80 with a small dash of XF-76 IJN Grey Green. Light Gull Grey is an very interesting color, a warm grey toned down with blue-green plus tint for scale and I guess there are many possible interpretations. In a month or so, I'm looking forward to a visit to the Naval Air Museum in Pensecola, Fl with my Dad (see avatar), so I'll get to see Gull Grey up close.
Glad I don't have to come up with a Dark Gull Gray tonight! Dflu 78, thanks for the offer...would appreciate your input!
Mike