I like those, and for $35 I think they're worth picking up a set (or two). But the problem is that Reno has really nasty winds that tend to blow through after lunchtime. They can gust upwards of 25 mph and those little discs would just blow around. I think we'll need real cones for it to really work, but I do like those little ones to use as "non-penalty" markers.
I'm thinking of taking the route of doing courses more like the police competition ones, but with not quite as many cones. And boxing the cones with gypsum like they do in autocross. It seems simpler than having to have a bunch of cones in different colors and having people have to remember that one color means go this way, another color means go the other way, and stripes on them mean other stuff. Just seems darn confusing.