The 8050 has another 2 teeth of total capacity compared with the 6870, but it's still only 39T, so with your 11-40, the maximum difference between chainrings would be 10T. If you used the 6870 and 11-42, that would narrow to just 6T, i.e. a half-step
I was running a 32/46 combo last year. I could customise the cassette so the high gears aren't so high. I still don't get how the other guys have set theirs up.
I'm sure I've seen people running 2x w/ MTB cassettes (@frank9755) otherwise I'd not have bought it.
https://www.youtube.com/watch?v=iNpdLrlN4HI
I've now got one of the newer RDs so guess I'll see what happens with both.
Maybe I saw people using MTB RDs?