"Do you guys think flipping the tips on longer bows, say 67 or 68" and longer, causes more risk of limb twist than it's worth?"
No, I do not. I think it will take away some of the set and perhaps and add 3-5 FPS, in addition to making it a smoother drawing bow.
A little limb twist is never a problem anyway and can be easily corrected if need be.
So go ahead and add some reflex in the last 8 inches or so. I've done it and it works.
Jawge