Peter,
Thanks for the reply. I have 60 rpm motors in both of mine, and a bit of aluminum tubing added to the arms of them, so agitation is more than adequate for the amount that is in there. They seem to come out nice and even. I also have a 3/4" aluminum lip, with a 1 1/4" chaff ejector above that, so there's lots of room for the quantity of beans that are in there.
I have been doing 454 green, and averaging 390 roasted, and those have been in the 15-16min to 2c range, 12-13 or so to 1c. Those have been nice and tasty. Based on the percentage weight loss I have been getting with those batches, I went 545g, and all 4 tonight came out to the 454g range, albeit a bit longer than I would have liked.
Ideally, I built these roasters with the end goal in mind of being to be able to do batches that are slightly over 1lb roasted (enough to give me a bit to try, if the batch is sold). 20 minutes does seem a bit long to me, compared to what I am used to, but like you, I'm not sure where the 20min baked idea comes from. That said, being that these are freshly roasted, I have not tried them, and I will likely not be trying them either. They are spoken for already.
Regarding the bottom heater, I have that on a switch, and I use it for pre-heating the roaster, and for a bit of a warm up in between roasts, but it is off for the duration of my roasts, so I suspect this may provide for a nice addition to push a roast into 1c a bit quicker. I had not even thought of it, haha.
By the way, I have been really enjoying this latest order I got from you. Thanks again Peter.