Have a close look at the meshes on some of your shaped nets. As moe says, start with 9 or 10 on the ring then add an extra mesh on the end of a few rows until you get it the width you want, then knit. Whenever you are coming back down to the ring again, knit two meshes into one. Shaping them also makes your roll of twine go further.
Good on you for making your own, it gets addictive. That rayon twine is nice to work with too, has a natural feel to it.
atb with the nets, and if I can help at all, feel free to pm me, and I will do my best to help.