Anyone used a FD-7800 on a compact? The spec says a maximum of 15t (a compact would be 16t) range.

Currently got an FSA SLK compact and FSA front mech, but it won't shift however I adjust it (7800 STI's), if I adjust the cable so far that it shifts into the big ring then the trip positions are so far out that it has to be in the inner trimmed position to avoid rubbing at the 11t end of the cassette! So I've concluded it must either be the FSA front mech is hopeless or the chainrings aren't stiff enough (option 2, but they're not yet worn so seems a waste to try those first and poor shifting isnt a univeral complaint withthat chainset).

7900's a 16t range if it won't work, but would like to make the groupset as a 'set' if it will work.