You would use acrow props to support the barrel maybe even 2 long ones to support the roof on the top bay.
Pvc windows would need to be fully reinforced with steel and the round baypoles would need to be jacked up to take the slack and weight, this is like a little gizmo thing shown here...
https://www.google.co.uk/search?q=b...SK0AWK24D4Ag&ved=0CAgQ_AUoAQ&biw=1024&bih=455
The baypole would need to be sunk through the pvc cill of the window so that it sits on the brickwork not a hollow pvc section cill, this applies to the top one also
Pvc windows would need to be fully reinforced with steel and the round baypoles would need to be jacked up to take the slack and weight, this is like a little gizmo thing shown here...
https://www.google.co.uk/search?q=b...SK0AWK24D4Ag&ved=0CAgQ_AUoAQ&biw=1024&bih=455
The baypole would need to be sunk through the pvc cill of the window so that it sits on the brickwork not a hollow pvc section cill, this applies to the top one also