This involves three different *A carriers, so I'll try my luck here before hitting the specific forums.

I'm booking a Eurobonus (SK) award trip on rather short notice, and on the days I want to fly there's no C availability, so I'm flying in Y on SQ (international) and NH (domestic & international). Since this is an award flight the fare class will be X.

So the question is, what, if any, are my options for upgrading individual legs?
According to How to upgrade on *A carriers, both SQ and NH block some fare classes from upgrading (in NH's case only if flying from the US?), but X is not listed. I'm willing to pay cash and take my chances with standby upgrades, although said willingness naturally depends on how much they're going to charge me...