Cliff,
Don't use PDCB at the rate that you suggest: - especially if it was designated
for toilet use.

-"My questions are, at long last, how many of the 4oz. cakes should you
use for each supper? Should I put one cake on every super?"

Even though in the past (last time was about 5 years ago) I have used this
substance in protecting against wax moth - I never used it in such industrial
quantities.
Then, I placed a small sphere of about 1.5 cm diameter for 5 supers.
Now, I am depending on the weather - leaving the piles of frames in supers out
in the frost - so far so good.
I suppose I loose 1 - 2% of frames each year to moth.
Others may indicate their ideas.
Peter