I used copper packing on my recovery still at 5gal scale.
Moved to copper column and condenser on my early keg based 15 gal still.
On both occasions that I tried recovering the last of the EtOH off the extracted plant material by distillation, the alcohol I got back was vividly blue. My assumption was Copper Sulphate. With the Sulphur presumably coming from proteins in the plant material (amino acids Methionine & Cystine).
So my vote would also be to stick with stainless.
Probably should have tried the GRAUS cannabis disorienter Supercritical420 & Future have been using. Washing Machine "Salad Spinner" tek
Couldn’t convince myself the wetted path was appropriate for Meds, couldn’t squeeze R&D funds to solve that from the ground up.
It never occurred to me to JUST use it for recovering the last bit of solvent. 
Looks like the CUP 15 has been ordered…