I have a related question.
I'm thinking of upgrading Y->C on my upcoming SQ25 JFK-FRA on 388 using two eVouchers (which I got when I made SEN for once a few years back) now that they will eventually expire. I'm now in H fare but happy to upfare to B if I can upgrade.
OP mentioned that D should be available, which is the case with my flight, but also said that they block upgrades to new business class using partner miles or instruments, so I guess I'm out of luck. Can someone confirm this? They do seem to release C awards on some dates according to KVS.
Thanks for help!
MtRoot