I have a compact crank running the 11-28. No problems at all. In fact, I am running the Rotor Q rings and even with that and a compact crank, the worst that ever happens (10-20%) on the fd is a slow, noisy shift (half a turn) depending upon the position of the fd and the big gap from the rings. With standard rings, perfect shifts every time. Not an issue, even under full load. I can't think of a harder test for a fd setup. Di2 is simply wonderful and you will have an extremely difficult time finding anyone who actually owns it, to have anything bad to say about it (outside of the cost). It's that good.