America West FlightFund (Discontinued Program) - What Fare Bucket Do Mileage-Deduct Upgrades Come From?

I apologize in advance if this has been addressed recently, but I was wondering what fare bucket mileage-deduct upgrades come from on HP.

As a CO flyer, I know that mileage upgrades come from a hidden fare bucket (R), but I am wondering what bucket upgrades come from on HP so I can do research ahead of time on a site like ITN.

Also, is there a comprehensive list of the each fare basis from First to Discounted Economy?

Thanks in advance for any help.