If you really want to be precise pins can absolutely be too big AND too bright.
Especially when you get below your top pin. There is simply no need to have a super bright big fat 30,40 or 50yd pin. How can you expect to hit a precise spot when you can't find one because your sight pin diameter combined with halo is taking up a foot of the target surface?
Pins should be getting dimmer and smaller as you go down the scale to your longer yardages. I have very short fibers in my 30,40,50yd pin sets and 1 extended green .019 in the top pin set which is also in the CENTER of my pin housing.
set next to a red .019 30yd pin this set up gives the illusion of having a single pin sight in low light (when you can't shoot far anyway) Makes things much less confusing to line up and see through to your target when a good majority of your shots might take place.
I will even have a hunting bow set up this year with .010 wrapped fibers for even more precision.