I am making my own cape pattern...

I had one prototype that was too small in the neck. I went and finished it anyway since I can just use the button allowance to give me two more inches of neck room. The finished cape is my prototype.

Here are the two pattern pieces. There is a collar piece not shown here.

This gray woven silk is going to be the finale. I made the neck bigger and had to add length in the arm area. I failed to calculate that fabric curving over the fat arms will cause you cape to slope up your arm.