I think if I were going to do a basic bug net I would just go with extra material.
I think if I really wanted to go all out on a bug net I would probably go with a zipper one side and then sew it in on the other side. That way I could throw the netting over a ridge line and zip it up for a bug proof setup. I couple of Velcro tabs on the sewn in side to secure the netting when not in use.
I would think that you would have to put Velcro around the whole parameter of the hammock to get a totally bug-proof seal. If there is a tiny gap in the netting mosquitoes will find me!