Are you saying that you use silver-plated STRANDED wire for
secondaries? Granted, AC resistance and Q are far less important on
the secondary side, but the notion of this wire being superior to
common magnet wire is incorrect. Stranded wire is inherently more
lossy at RF frequencies. This is because the skin effect causes
current to travel on the outer surface of the bundle. If a strand on
the outside of the bundle weaves to the interior of the bundle, the
current in that strand will try to find its way back to the surface,
and this means traveling to adjacent conductors, through any
resistive oxide layers between them. This strand-hopping results in
a much higher AC resistance than if a single conductor were used.
This is the reason that Litz wire insulates the strands from one
another.