July 11th

perfect timing. Gives time for CKB to smash the UK on its own. It would probably peak by then.
I expect Fly to be released in June right after SuperBass. I don't know why you guys think her singles are messy. She's an urban artist their singles don't need to be structured because urban radio is not like Pop. They play what they want to play. They will spin album cuts like their singles.
Super Bass to Pop - mid April
Peaks late May.
Send Fly to Pop - Mid June
Avoid clashing with Rihanna's original single as much as possible. When CKB peaks Fly should be gearing to take off. They should send it to Urban first though to pick up the extra AI so that getting the #1 on the Hot 100 more achievable.