why are you trying to hit Lats with bench/flyes when you could be using BBRow or Lat Pulldowns? unless you're talking about reverse cable flyes, these are not exercises that will/should directly target the lats but rather activate the lats as a result of targetting other muscles. Try using the Lat Pulldown to isolate your lats and you'll watch them grow :)

best of luck!

Are you sure? Did you try this yourself?

 I do lat pulldowns to the point of failure 3 times a week and have noticed significant growth. Also do dumbbell rows 3 times a week and I think they have really helped as well.

The best way to grow them lats is PULL-UPS! Try doing some weighted negatives for them!