Yeah, but essentially I would think there'd have to be F inventory on both segments before EUA would clear at all. You're probably better off having the ticket split into two separate flight segments, you also usually get more miles.

I did this on AA from LGA-MIA-POS (that's Port of Spain, Trinidad). They have a one-stop LGA-POS, but the front of the bus is considered J (business), so you only get 25% bonus miles. By splitting the ticket, I got the First Class bonus (50%) on LGA-MIA, and I got a lot more base miles because MIA is a little bit out of the way geographically.