
I'll agree it's going to be difficult to say. You only have to look at all the Labrador x Poodles which - their breeders claim - will be a size in-between the two, but end up taller than both parent breeds.
I had a neighbour a few years ago who bought two puppies, from a litter born to a Pointer (I assume GSP), father was said to be a GSD, but I think that was deduced only because they had upright ears. Once they matured it was very evident they were sired by a Siberian Husky as they had a lot of the body shape, angulation etc. in common, as well as a few hints around the tail carriage.... not to mention the bog-off approach to recall! They were both jet black - and about the same height as a husky.