The heating and forming the button is how I was told to do it from CVA tech. And the fiber just fit thru the holes in the sight so the button does not have to be very large. Just slightly larger than the normal diameter of the FO.
Anyway, I normally put white out on my red fiber optic sights. Reason is the same as Muleys. The red appears to be a blur or double image for use old farts with poorer eyesight than our younger counterparts.