This might make your scenario seem a little bit better. The majority of the FRA-IAD flights are often still on the old C seats and they are all day flights. I usually worry much more about overnight flights on SWU's then not, but that's just me. Also, I would think that you should focus on the FRA-IAD flight only. Kiev to FRA and IAD to BOS aren't really worth worrying about using such a valuable upgrade instrument on.