I've been, unsuccessfully, trying to do this (I'm silver, partner is Gold, separate bookings). The regular call center couldn't even fathom what I was talking about when I called; my partner has been on the phone for 45 minutes at this point-- solely to try to TCP our flights to put me in row 1 next to him on the shorthaul segments. It is getting to the point where we will have spent longer on hold/phone than the flights in question!