One thing I've done is look for alternate flights in which F is wide open. Often the refare is worth changing flights. And of course you get LPs for the higher fare. But there's a chance those open seats are suddenly gone so there is a risk. For Friday I changed my MIA/PHX flight for an additional $75 as there's eight F seats open on a 321neo. No upgrade yet but hoping the $75 gamble pays off.
Even a few times when I refared into F it was only $200-$300, like my flight tomorrow.