Here's the rough cut of the cowl, from two panels of that same foam floor matts people use to make cosplay armor and glued with DAP contact cement.
Here I'm bevelling all the edges, using a dremel sander bit you can see some are just rough, while others have already been smoothed. I'l also carve some radial fold type lines with it as well.
Here's the finished cowl before paint, and attachement to the foam harness. Its about 40" wide, by about 40" tall. Once curved, it'll be about 18" tall in the back.
Here's a test of the head on the cowl, with the fronts curled in and glued down.
Here's the harness/cowl assembly. The front edges of the cowl are attached with contact cemented strips. The back is connected with folder coat hanger wire, attached to the cowl with contact cement and a fabric contact cement soaked strip. Its attached to the harness with another foam cut over L bent ends, to make it stronger, and support the cowl weight. (Granted it isn't much, but it catches wind!)
The first attempt I made at attaching it failed, because there just wasn't enough support in the back. I tore that down before the contact cement completely cured, and rebuilt it today, this time using a folded over coat hanger for support.
Here's the cowl with a final working attachement to the harness.
There! The cowl is mostly done!
Because its bendable, it can be posed on the mannikin, or on the costume while being worn.
Only real things to do now are a back cloth bit to cover the harness, rag up the fabric at the bottom and the sleeves, and the ragged shoulder drape (Like what you see on a duster coat.) WHEW! I thought that cowl would be the death of me!