Ok, I admit, it's been a while since I've had any status AND it's been a longer while since I've purchased a full Y that's upgradable if you're an elite.

I just did, and the upgrade process worked beautifully and seamlessly.

I made my reservation, went back into it, and there was the nice little check box to request the upgrade to F. I did so and the system reassigned my seat to an aisle in F, based upon my preferences.

I'm sure you've all done this lots of time, but it was my first time, and worked perfectly. ^^