it might be worth a call to aa or vt about the award using aa mi, either as lax-ppt-rar-lax or lax-ppt-open-lax which is the basic problem....if its ok, there should be no prob adding sfo....

also, check the rt fare ppt-rar, maybe its not much more than the 1 way...

edit to add....i would call aa & ua/co to make sure that 1 way awards can be used on your trip....

edit again...i just searched the aa forum for tahiti....it shows a lot of threads & is over whelming, but w/ patience & fine tuning, it might help...