Adding a window to your bivy.

I would like to add a nanoseeum netting window to the hood of an old ti goat bivy. Has anyone ever done something like this?

I plan to cut a small rectangle out of the dwr ripstop fabric of the bivy and then sew in the netting but I just can't quite picture how to do it without ending up with a bunch of unhemmed/unfinished edges. Is there a simple way to do this so that the edges of the window are clean and look nice?

Any thoughts or advice would be appreciated.

Thanks!