I would add some type of lightweight sewable interfacing. This chart has more answers than you have questions.
https://www.joann.com/on/demandware....acingGuide.pdf
Edited to add: I would use an iron on. I'm not sure how thick the 906F is. It was the first one I saw that was iron on aka fusible and wasn't on the bias. Since it isn't woven, it shouldn't stretch which is what you want.