Why would someone want to keep playing around and modifying a successful pattern?
For myself, there are a number of reasons. One is that it is a good excuse to go fishing, the new pattern needs to be tested. Another is that I just think its fun. And lastly, you could come up with a pattern that catches more fish. My prime example of this is the Yellow Peril.
A friend asked me to tie up a bluegill fly that he had been given and was out of. The description was a brown biot tail, yellow body and a bead. Not a lot to go on, but I tied up a few flies for both of us and fished them. And we caught sunnies, lots of sunnies, but nothing else. That’s fine, but I wanted more, so I played around and added a red collar. And we caught sunnies, and crappies, and perch, and bass. That simple change had dramatic results.
The red collar also helped to name the fly. The yellow body and red band around it reminded me of the Stearman biplane that a friend has. It was a WWII naval trainer that was nicknamed the Yellow Peril because of the number of “incidents” that student pilots had in them.
So go ahead and tinker with your flies, you never know what will happen.