If you want to stick with doing reverse flyes after barbell presses, do me a solid and at least make one modification. There are few things that drive me crazier than a lifter who doesn't respect the point and purpose of accessory work. As a result, these disrespectful lifters use dumbbells as heavy as those used for major work sets, use a ton of body English, and somehow believe gains will follow.
For the record, any flye pattern counts as accessory work. Recognizing they're intended to help the shoulder perform better, bring up weak links, and possibly bolster bigger lifts should move a lifter to lower the weight, chase more reps, and focus on form and technique while getting their pump fix.
Not doing this results in a miss for people trying to target the rear deltoids and can often result in anterior shoulder glide, which is another can of worms for shoulder health.
Switching to a reverse grip on flyes can negate these problems since its makes variability in start and finish points much smaller. Because of this – and the fact that externally rotating the arms makes them contract more strongly – the rear delts get hit harder and more effectively through the entire set.
Done properly, there's simply no need for most lifters to do this with much more than 20 pounds.