No chance.... There is hardly any tension at the top of a fly with dumbells..... If your not able to keep tension on the chest during a pressing movement at the top I'd advise you learn how to..... Start by retracting your shoulders and contracting your traps hard during the movement....
Decline Dumbell Press has been shown to stimulate the most pictorial muscle fibres than any other chest exercise.....
Most guys who moan about needing more upper chest just need more chest.... They are lacking a chest, not an upper chest lol
If you can do declines effectively they are probably optimal for overall pictorial recruitment