If I have a normal R/T rewards reservation that will be using EVA metal (booked with the funky 24 hr wait and see reservation method), is it possible to modify it to an open jaw w/stopover? So... SEA -> TPE -> SEA -> IAH. I believe, in typical reservation situations, it'd just be a $75 add on fee, but since I had to jump through a small hoop to make the original reservation, I was wondering if it'd be different.

Also, can a normal reward be converted to open jaw w/stopover once the first flight has been taken?

Thanks