The issue here is that parasolid (underlying kernel of SW) does not allow you to knit 3 surface bodies together anywhere with any feature or method in the SW system. that is because most everything in SW is a means to a solid model and 3 surface bodies edges (infinitely thin bodies) knitted together is not a physical reality. Really depends on what you are doing with this and where you want to go with it. Is it going to eventually be thin, solid walls? If so, use to extrude thin features; one of the outer perimeter and one for the inner 3 walls. Better yet you can do one hex thin solid and pattern it.