On the back of the orange (O) card are the B-17: Errata and Clarifications. Number 3 states:
"Table M-2, under Note(a), "FE 190" should read "FW 190". Also add:
2 or more FCA = FBOA
2 or more FBOA = Destroyed
FCA + FBOA = FBOA"
Hope that answers your question. There are no cumulative effects on the German fighters - FCA-1 and FBOA-2 remain the same.
Great! Thank you very much for the info. I guess it helps if I look over all the cards more thoroughly.