That's an idea - I've seen that stuff on road construction sites.... I'll have to check about the wooden posts... Do you think those posts you can stick into the ground with your foot would work? Or would you need to dig with post-hole digger and use larger wooden ones? Thanks again for the idea... we really need to isolate him from the other horses to make progress....
Temp posts are really flimsy. It wouldn't have any strength, and they'd pull in toward the middle.
I'd do it with wooden rounds, and I'd tip them out slightly. Having the posts angled out a little serves to save you from getting a knee mashed against them, but also protects you a little from getting impaled on the top of the post. I'd run the netting two rows high and cut the top of the post even.
I think you'd only need 5-6 posts, a pentagram or hexagon would be nearly round enough, and the span between them could probably be 15 feet... maybe.. if the netting was pulled nice and tight. Still thinking through how to do the gate opening, but I think the same netting could be used, and hooked and unhooked somehow.