I own two Cobra sights and haven't had a problem with either one. I even had the fibers out of their housing for about 30 minutes, trying to get them back in line after putting the sight light on with no problems with breakage, whatsoever.

What are you guys doing with these sights to have the fiber break so easily? I am sitting here playing guitar on my old 3 pin and can't manage to break them.

I plan in the future replacing the fiber with Fitz, but it isn't because of a breakage concern, rather I know they are a bit better quality fiber.

As far as turning the 3 pin sight into a 5 pin sight, shouldn't be a problem with the pins, but like Kodiak said, you might not have enough room for the coil of fiber optic. You might get away with coiling the strands tighter but let me tell ya, it is kind of a pain to work with.

If you are going to make all of these mods, I would suggest looking into Fitz replacement fiber optic for your sight. Supposedly brighter but I really can't see how since Cobra sights have about a mile worth of fiber wrapped inside the column.