the 2nd tube (vacuum)
when you say you blasted it with the vacuum are you blowing down this pipe?
Or does it just "vent" the chaff as the hot air come out.
if you added a internal elbow pipe above the lid into the vacuum and introduced a stream of "blown" air do you think you could generate a vacuum effect that might assist chaff removal?
this way you would not be introducing cold air to the roast chamber as much.
Interesting idea but, I like your nicko pen cutting line, dont want any errors :).... i use the same techniques. I had a laugh
you going to drink that 1k of coffee you cooked :)