Last year I too put up a 9 x 5 foot flag and needed a big pole. I used 3 five foot sections of 2″ PVC coupled together w/ pvc couplings, duck tape AND I used a 2 foot long by 1/4 inch thick by 2″ wide aluminum stay at each of the 2 couplings for extra support. (The wind wanted to snap the PVC at that height.) I also drilled a couple holes for guy lines and we used lots of rocks to stabilize and support. Once it was up,,,,it stayed for 21/2 hrs out straight!! It was awesome, we were on Moosilauke. Good luck!
Re: Big flag-big pole! Jayne