I have logged the Gerber files for PCB of EMG sensor. There are three version of 26x50 (mm), 31x16 (mm) and 22x22 (mm). Choose the one that fits your usage. Currently I am building an EMG bracelet (yes, similar to the myo armband currently available on the market. I just want to build one for me from scratch) so I am working with the 31x16 design.
Here are some pictures: