Dual top loads

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Original poster: "Todd Reeve" <todd.reeve@xxxxxxxxxxxx>

While checking out pictures of coils different sites on the Tesla 
Coil Ring, I noticed that some of the coils that use flexible 
aluminum ducting for a toroid sometimes have 2 stacked toroids while 
the coils that have a spun aluminum toroid have only one.  I surmise 
that this is to increase the capacitance of the top load.  Is this 
needed when using ducting since the wall thickness of ducting is thin 
compared with a spun toroid?