I recall that if you use the kiosk to SDC, it will basically blow away any upgrades you may have gotten even before you confirm that you actually do want to change. However, what if you SDC with an agent? E.g. let's say I'm on YUL-JFK-SFO, and I decide I want to take an earlier YUL-JFK flight so that I can schedule a global entry interview in JFK. If an agent processes the SDC for the YUL-JFK flight, will I lose my upgrade on JFK-SFO?