Really extreme American Trap guns are designed to shoot 70-30, or even higher. Some people shoot nothing but competitive American Trap, so they use a gun designed specifically for it.
With some of these guns (e.g. some Ljutics) you actually "float" the bird, meaning you shoot with it appearing to sit a foot above the bead.
There are, of course, problems with this. If you shoot a gun like this all the time, you will have a very hard time grabbing something like an 870 or a regular field O/U, and hitting anything instinctively with it.
WRT the length and weight, dedicated American Trap guns are designed so that they automatically swing at a certain speed, and sit comfortably near horizontal at the set. Since the targets are thrown to the same height and a regulated speed, this makes them easier to hit.
Again, such a gun is nearly useless for other targets, but it makes hitting 100 straight almost effortless for a skilled trap shooter.
Remember: the hardest thing about American Trap is that most people let their mind wander and get fatigued after a while. The idea is to make the sport into a sort of simple meditation. Set, call, swing, slap trigger, next.
If you're getting the idea that competitive American Trap has gotten to the point where it bears little resemblance to the hunting practice that started it, I believe you're quite right. It's a sport in and of itself.