Traps are used by Optis all the time. Weird the first time you see one, but very straightforward and easy to get used to. I've been pushing (here) to use them when you have big cat regattas, with everything from Waves to F18s on the same course.

They aren't really "hard" to keep square, but do require a lot of (very good) mark boats. Timing of the fleets is the main thing. It's easy to get stuck with a mark that needs to be moved, but can't, because there is a fleet coming to it.

Mike