Graywolf said:

I'll shielded the vacuum inlet against direct splatters, so splatters inside the drum are ostensibly of minimal concern, because much if it gets washed by the rotation, but vee shall see...........

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You may also get some poor distribution along the edges due to the squared corners of a drum design--an elliptical container would do best in absence of the spherical shape vs. a cylinder.

Well... my system works like a charm. I can load about 1/2 pound of material into the column, inject soak, wash, boil off the butane, switch to purging - cake. So far my best run is 5% yield by weight but its mostly likely the material I am using, which is trim, small flower and all leaf processed by a centurion trimmer. One run yields about 14g of concentrate.