Thanks saftfrucht and ArcherII. I'm going to try an experiment and verify this. I've switched almost half of my B777s to an all standard configuration and so my fleet now looks like this:
2 x B772: 270 Y, 48 C, 10 F
1 x B772: 300 Y, 40 C, 5 F
4 x B772: 250 Y, 30 C (premium), 4 F (premium)
1x B773: 340 Y, 64 C, 10 F
3x B773: 350 Y, 25 C (premium), 10 F (default)
I'll give it a few game weeks and let you guys know.