Arghhhhhh.......vinyl problems! (Recycled Reese's wrapper coupon pouch)

I was totally frustrated this morning while sewing another vinyl pouch. I had used the 20-gauge vinyl (vinyl on the front and back for each sheet of recycled wrapper). The sewing part was easy peasy....I usually sew it the way I'd using regular fabrics (sew on the wrong side of fabric and then flip out to the right side).

The cutting/sewing took me altogether 10min the most and I spent another HOUR(!!!) trying to flip it out......geez. In the process, I poked myself in one of my fingers till it bled and I also broke a nail. And despite all my efforts.....the corners still looked like these.......

I tried various things like rounded the corners and made small V-cuts on the rounded corners, I also applied talcum powder on the vinyl so that it doesn't stick.....but still it's super duper hard to make the corners look nice. Anyone with tips for me please??? I'd be eternally grateful. My last resort would be to redesign the pouches or perhaps sew on the outside such that I don't have to do any flipping. But I really prefer a cleaner look with stitches on the inside. So HELP!!!!

Anyway, here's how it turned out. I like the see-through part!

And despite the ugly corners....the pouch still works in all the ways that I have wanted it to...so I can't really say I'm not happy with it :P