Have you ever tested to see how much effect plastic might have? I'm planning to use Sterilite containers as my QT tanks. They are cheap, which is great, but with my physical handicap they will be soooo much easier to setup, take down, sanitize, etc. Plus, they already have lids. I'm less worried about copper because I can test for that. Maybe I should start with a little higher dose of CP when quarantining with CP?
I've dosed copper into "Sterilite QTs" and absorption was moderate. I'd say if you dosed CP @ 60mg/gal you should be OK.