Very useful thread to thanks for the OP for starting it!
One quick question, I have a GUF2 booking travelling F out and J back, I used amex to book the flights and on MMB it shows the tier points and avios for F and CW (I have booking classes A and I)
Would I still be able to upgrade the return leg with avios, like normally, or does the GUF2 change the fare class rules?
TF