Now after a month I finally have the "real" answer. It was possible to do this before the PSS migration. However, the system can no longer issue a RT UG on separate TKTs. In an UG booking where I asked them to TKT a month ago, an agreement had been made between MPO and me. I would drop one of the sectors, and they would issue the reward as 2 one-way UGs and then re-credit the difference to my account.