I have worked with testers 9 hours off my schedule.
That worked out very nicely. We developed during the day, sent out a mail with test instructions, went home, and had a mail message with test results in the morning. So, it felt like you never had to wait for test results.
9 hours also isn’t too large a difference for the occasional phone meeting (one side would take the call from home, either before coming to work, or after getting home, and would take compensation time typically on the same day).
It does require people in both teams who can write clearly, though.