Suppose you have a full-grown (or is it fully-grown ?),

Either.

 german shepherd.

Would you characterize it as {qovIj} or a {ngavyaw'} ?

I'd characterize it as a dog or German shepherd. If I had to name the closest Klingon equivalent, it probably doesn't matter whether I pick qovIj or ngavyaw', since it's neither.

If I had to pick one... it'd be tough, since I don't really see much of a size difference between Kruge's pet and the animals seen on Rura Pente, which is what we're told the difference between a qovIj and a ngavyaw' is. Kruge's qovIj has much less fur than the Rura Pente beasts, while the Rura Pente beasts have tusks that the monster dog doesn't have.

For simplicity I'd probably call all little drop-kicks qovIj and use ngavyaw' for big dogs. But I don't think this is ideal.

And lets say, you have a {ngavyaw'} puppy..

Would you characterize it, as a {ngavyaw'} or a {qovIj} ?

Or would you play it safe, and say {ngavyaw' ghu} ?

And, to take this to the limit..

If you had a {qovIj} which took steroids and grew the size of a small
car, how would you say it ?

On the contrary, if a {ngavyaw'}, matured chronologically, never
attaining the expected size, but remained very small, would you still
call it a {ngavyaw'} ?

I think qovIj and ngavyaw' are names of specific species, so it doesn't matter whether they're immature or stunted.

-- 
SuStel
http://trimboli.name