hi folks,
we have currently booked (not ticketed yet!) FRA-JFK and PDX-FRA in I-Class.
I'd like to fly in O on the PDX-FRA segment but right now, only one seat is available (as usual) but let's face it: usually there won't be 8 people paying for there seats

.
I will have to ticket that reservation next week. What can I do afterwards?
If the seats open up and I call LH, will they charge me 25.000 miles per Seat (as per a split booking) or 50.000 (as per a regular upgrade)? Will I have to pay 2*40 Euros for a change of the booking? Will I be able to change it at all?
Thanks!
Ben