you make an excellent researcher, please let us know what you find.Of particular interest would be instructions which are *NOT* included in the publications surrounding the construction details for the OPTx. Techniques surrounding the actual winding.
It is one thing to say, "lay down __-layers of bifilar 19 ga wire in the first layer".
It is quite another to explain some of the pitfalls one would encounter whilst actually winding the coil.
cheers,
Douglas