I didnt mean to cause any grief. I have been heavily into these old bird for the last decade plus only so i dont claim to be an expert. I mentioned it as its been the way i have understood it to be for some time but that doeant mean im necessarily right. What i see is at best an educated opinion but there may have been different ways so build what you want .
I have also been fascinated by them for a long time, and have wondered about many of the details. I think I have interpreted the legs correctly based on what makes sense, supported by what is on the ski 'planes.
If you use the two tubes as shown, one coming straight down and one sloping from the back, you automatically get one of the faces of the slot for the axle. then you need something to stop it flopping out the front, that explains the round topped bracket with a bar down the front. If you extend the sloping member forward, you get somewhere to anchor the bungees.
In my opinion that makes a very simple and strong structure, especially when the legs and the centre vee (for the rigging wires) are tied together with a simple bar.
Putting in a slot between the legs makes sense on the early aeroplanes with the sloping leading leg, on the later ones, it just complicates things and doesn't explain that front bracket
As you say, in the absence of some contemporary information, its all about interpretation. And my interpretation happens to differ from Ian Stair's for the reasons above. I wouldn't like to say mine is right, or that Ian's is wrong for that matter.
Thanks for replying, I appreciate it. And apologies for getting in a bit of a snit over it - anyone interested in these peculiar old birds must have an appreciation of the finer things in life. There are clearly at least two of us!
Richard