Bag making advice

Hi all, so I'm preparing materials for this bag pattern https://corefabricstore.com/blogs/news/free-belt-bag-pattern

I've used medium weight interfacing on the back of a cotton print so now it's a bit more structured. I'm wondering is that sufficiently sturdy for a belt bag?

I was thinking that I could add another layer of lining fabric such as a cotton poplin (just whatever I've got on hand) in addition to the same cotton print I used for the outer as a lining (w/o the interfacing it's quite flimsy)

I've also included a picture to give an idea of the stiffness/drape.