Climate/shipping adjustment, separation anxiety or sick?

[rlma]

Our 11 month old male (un-neutered) GS came from Ethiopia this past Saturday with my father. When he left Ethiopia, he was deemed totally healthy by his vet.
Now that he's here, though, I'm getting a little worried. He just isn't very energetic. Before we got him, I pictured him being pretty hyper and high maintenance. He's the exact opposite though... he lays around the house without a peep. He does play with us (large rubber balls and tug toys) but acts like a mature dog instead of a puppy/youth; polite, never silly, never nippy, always does what you ask of him (like "leave it"). He's eating fine and going to the bathroom on a normal schedule, and his poops look fine. He seems to drink enough. He seems to breathe a little heavy, but I don't know if that was normal for bigger dogs.

In any world is it normal for a GS youth to act like this? I was thinking reasons for his behavior might be:

a) he's recovering from the stress of being shipped, or perhaps the climate change from Ethiopia, even though the climates between here and there aren't that terribly different. Or maybe a little worn out by the change in scenery in general.

b) he's a little stressed from not having my dad with him 24/7, though the only potential signs are looking out the window.

c) we haven't really exposed him to any of our dogs, since we'd have to go outside and it's been so rainy that our whole yard is flooded. Maybe he'd perk up if he had doggy friends?

He seems happy and alert, so am I just being overprotective? He wasn't supposed to go to the vet until he's neutered in a few weeks.

Thank you!