Jami,
here is the link to my Frøken Sørensen sailplan (dimensions on p.2). The 22mm battens are a bit on the light side for batten 1 and 3, but otherwise I hit quite well.
I have made three yards, so far with two tubes on top of each other. I aim for a main tube which should be almost stiff enough to cope alone, and then I add an upper tube from the same dimension as the lower battens. This has proven to hold up well without getting too heavy.
I tie the halyard to the yard with some sort of rolling hitch. After a little practice, I have found it easy enough to keep the yard from twisting on its side. However, I would not make the yard from two equal tubes, as it will be too weak sideways (or too strong and heavy vertically).
I only bolt the two tubes together at the ends. This is where they take up most shear forces, and besides, I don’t want to drill big holes near the middle of the yard where stretch and compression is highest. In fact, any holes in the yard is closer than 50mm from the ends.
Arne