Tom, not sure if this went forward or not. But Altelix (one of my favorite outdoor enclosure suppliers) has just came out with a pole mount VESA bracket.
They say it will hold up to 45 lbs. And can get mounting straps to fit up to 13" poles.
There are mounting adapters online to go from VESA100 to VESA200 if needed.
This should work for up to a 55" easily. Possibly a 65" as well.
[Link: altelix.com]