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I'm trying to print this part : gpm_double_triple_ext30_rotated.stl

I have problem with the middle and top prongs (flanges) on the end that has 3 flanges. If I print the part the way it sits (without rotating) the middle and top flaps have no support. I tried turning on support in Slic3r setting, but I don't see any gcode that would produce the support.
How am I supposed to print this part?

Thanks very much