Problems with my Pouch

Following yesterday's reverse applique, I thought the fabric would work well as a wide mouth pouch.  I found Anna Noodlehead's fab instructions, but my fabric piece didn't quite lend itself to her method, so I bodged it a bit

The pouch does everything it's meant to:

It looks fab

It opens really wide

But it's not quite stable!

I suspect its because I made the fabric into a tube, THEN added the zip,and I guess I've distorted its shape, but it does hold whatever I want to throw into it, and I do love the grey / red combo