I once rode transcon EWR-SFO in a 752 with BF seats. I was a lowly Silver at the time an got the Upgrade at the gate. I was on a K fare. It certainly is much better than sitting back there for 5-6 hours.
I ride IAH-GRU a lot, but NEVER in Coach, so the transcons are a sort of walk in the park for me.
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Do not sit in the back.