Originally Posted by
Smyrnaflyer
I think you can ask the to apply the RUC only to the JFK/LAX segment. I've done this with international flights when I got upgraded only for the domestic portion with the free upgrade.
OP wants to be able to easily SDC the whole trip. Using the RUC means that the OP can SDC into any available FC seat and keep the upgrades. Otherwise the segment with the free elite upgrade with SDC into coach only if the original coach fare class is available and become SDS otherwise.