Northern Chinese or Indian giant Flying Squirrel ?

This flying squirrel was seen at night near Ruoergai in a coniferous forest in a place they called Baxi (a local nature reserve) in Northern Sichuan province. This was at about 3,200 m at the upper limit of the forest. It has an all black tail, light underside and light  and is a large sized flying squirrel (i.e. two times bigger than a north American grey squirrel) . The local guide had no idea what species this was but we thought it might be Northern Chinese Flying Squirrel   Aeretes melanopterus or Indian giant flying squirrel. Any ideas?

Stuart Chapman