A few tips to make incline flyes more effective:

1. Get your upper back off the top of the bench. This allows the scapula to move with more range of motion, allowing the pecs to get into a more lengthened state.
2. Keep your palms forward and bring the dumbbells back toward your ears, not down to the side of the body. This also puts the pecs into a deeper stretch.
3. Use only a slight bend in the elbows. Most people get way too much fixed elbow flexion with flyes, turning into more of a half press/half-flye type of movement.