Creating a baseball uniform from the early 20th century was something I had not delved into before. My original plans were to make a grey wool flannel suit as a copy of the original Hennessey uniforms, and a ivory/blue chalk stripe wool flannel that would represent Carl May's time with New York. I happened to have a piece of heavy cotton chalk strip that looked pretty correct so my first "test run" of the pattern was made up from that.
Fortunately for me I found a great article written by the gentleman who authenticated the jersey before it was sold. If you go all the way to the bottom of the page you can get full pics and the process behind the documentation of it. This was more help than I can possibly relay to you in getting a "right look" for the uniform.
Thing that were different on the 20's uniform were a front that opened all the way to the hem, and a "sun collar" (a short stand up collar) and facing around the neck and down the front. I had already worked out how this would work on the cotton sample so adapting it to the more forgiving wool was very easy. For those of you who don't sew with much wool, it can be pretty easily steamed into shape- so awkward curves become less problematic.