Are the rudders not to far from the stern? Its he the first time I see this.
Well, you should look at Moth
to see how far they do hang their rudders, Wayne's is fairly sedate compared to those
Note that the reasons for those long gantry are different: The Moth want the rudder way way back because it will reduce the size of the T-foil as there will be less weight to lift due to the increased lever effect. Or something.
On the skiffs it is as far back as possible so it stays in the water when they fly their ridiculous spinnakers which are pulling the whole boat out of the water (kidding, it's because there is a better undisturbed flow further back, the smaller the boat, the longer the gantry. 12' skiffs
As for Bitza there is not enough space between the rear beam and the transom to fit the tiller bars.
It's all perfectly legal, the rules only limit the hull length, and as long as they are not buoyant you can make the rudder gantry as long as you want...