Thanks for your thoughts - gosh, you all aren't competitive, are you?! Anyway, at this point it seems that the deciding factor would be where do we spend the majority of our time. For all the other criteria:

"Factors used to determine main home. In addition to the amount of time you live in each home, other factors are relevant in determining which home is your main home. Those factors include the following.

Your place of employment.

The location of your family members' main home.

Your mailing address for bills and correspondence.

The address listed on your:Federal and state tax returns,

Driver's license,

Car registration, and

Voter registration card.

The location of the banks you use.

The location of recreational clubs and religious organizations of which you are a member.
"

I can verify that my US address is used for everything listed above except for the last one, but that's only becuase we don't belong to any clubs or organization. And yes, we do live with a relative in the states - our clothes are there, our 'stuff' is there, I cook there, do laundry there, etc., but it's still our home in the states even th we don't own the property.

I'd still like to see the form that will be used to determine eligibility for this credit.