Nope. You only have 120 degrees between each fletch with a 3-fletch. With two fletches set at 75 degrees, you wind up with an included angle of 150 degrees, top and/or bottom. 30 degrees MORE clearance. Of course that puts the other two fletches with only 30 degrees between them, so that's why they're set perpendicular to the string. If you can't visualize it in your head, I'll borrow the example LBR used above. It's almost exactly the same angles I'm talking about.
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Art, maybe I'm loosing it;
From your example, the angle created at your less then, and greater then symbol would be 75 degrees, the angle from created at the top and bottom would be 105 degrees. 75+75+105+105=360. 105 would be less then 120, so I would assume you would get better clearance from the 3 fletched 120 degree arrow.
Please explain how you get to 360 degrees from your example. I think that would clear things up for me.
Bob