CX does not allow seat assignments until 5 months before departure. (if memory serves). To get those seats in the FC cabin, call CX in the USA 800# and request those seats. Assuming you have paid tix, you'll have no problem getting them assigned. I have done it while traveling on a paid J ticket and had no problem reserving the seats. Kindly remind the agent of your OW status. Hopefully, they have not changed the policy since this summer! BTW, same J service, food, and beverages just in FC seats. ^

Cheers!