3) Can you easily manipulate it in the water?
The short version…action. Can you impart the action you want into the fly, and does that action trigger fish into eating? If the fly can’t do this, I won’t fish it. To me, this is the most important part of the equation. If a fly cast well, holds a good profile, but swims straight back to the boat, it will go into a pile of flies I will never fish again. I want it to look panicked, weak, and/or dying. Too much material is something that can prevent action. You don’t want to drag a wet sock through the water. Adding weight to the back of the fly will help force a side-to-side, or erratic motion. Think about pulling a trailer overloaded with wood. If you try to stop too quickly, the weight of the trailer pushes the truck forward. This results in the jack-knife effect. Now think about building a fly. If the back drives the front, it won’t swim straight…which is what you want.
A muskie’s metabolism is low by nature’s design. This means its feeds less often, making it more difficult to catch. A muskie does what it wants, when it wants. It doesn’t have to make a snap decision, but you want to encourage a mistake as much as possible. Trigger that top end predator instinct. A muskie often follows a fly without the intention of eating it, but while you have its attention, try to trigger it into doing something it didn’t necessarily plan. That’s hard to accomplish if your fly continues to be predictable. A prey fish that isn’t wounded or panicked typically swims in a predictable fashion. Be unpredictable.
Muskie fly tying and fishing isn’t for everyone. It’s a grind mentally and physically. Its borderline reckless and dangerous in the sense that it can consume you. But the rewards can be some you won’t soon forget.