Hi Paul. Happy New Year.
     I had the opportunity to use some plastic excluders sometime ago
and I opted from throwing them away.  They were ineffective in keeping
the queens out (the same was true for similar metallic excluder in sheet
form).  I prefer metallic wire excluder because they do the job and are
easier to clean when they get clogged with burr comb and propolis.  BTW,
to clean excluders, I just hold them over a flame and melt the comb or
propolis.
I hoe that this will give you a bird's eye view on my opinion on
excluders.
Best regards.
Dr. Rodriguez
Virginia Beach, VA