I remember seeing Rian Johnson comment on one of the many Osh 25 Videos about the RV-15 that CS4-4 rivets would not be a suitable replacement for the LP4-4 rivets from a strength perspective.So for those wanting a flush riveted airplane but don't want to add a lot of additional build time, flush blind rivets would be the way to go.
The Heads of the CS4-4 are very thin compared to the LP4-4