Planning in costuming is a critical part of making the actual costume. Good planning is an excellent way to prevent many problems and mistakes that can occur during construction. It will help gauge the cost and time to make the costume as well. This is very helpful for costumes that require a frame and/or function. In such a case, wings.
Wings commonly are supported with a frame hidden within them. The frames strength is determined by estimating the amount of material used in the wing with durability in mind. Why the extra durability? At some point they will be shown off at a convention crowded by people and obstacles that will most likely be bumped into accidently. This includes taking into consideration of points that may fail, such as a joint which would be wise to reinforce.
The best process to follow when planning may sound obvious and simple but… it is. Pencil and paper, sketch it out! Your ruler is your friend. Why? Scaling. Accurate dimensions of the drawings help solve sizing problems, which in turn; help judge material and help form the best plan of attack. If possible, full size drawings tend to be the most useful. This for the simple fact that not only is this drawn to size, so math involved in scaling, but can be cut out and used as a stencil.
Even better! For the people who fret over symmetry, like me, we all know that paper can be easily folded and cut symmetrically. A good example is when made a pair of tonfa props. We drew out a profile, made a stencil and cut out exact mirrors of each other. This is also useful for reproducibility; for instance if someone needed to cut out a gazillion little bows for a dress or scales for scalemail, very useful.
This compounds when working with a group of people: this helps coordinate as a group bringing consistency in the parts being produced. A drawing or stencil is easy to store as well for later use. Lastly, but the most cost saving in my book:paper is far cheaper than any costume material. Cutting out a paper stencil and messing up is far less costly and painless than say cutting out a piece of worbla and messing up. In conclusion, I look at it like a war being waged; Any smart general will definitely have a plan before the first move.