I just did an 8x10 in a unicolor drum. Caffenol (4 tsp instant coffee, two of washing soda and one short tsp of Vit. C powder in about 8oz. water.) -with a tiny splash of old dektol (thanks, John). I shot the film (old txp 320) at box speed and let the drum rotate for about 20 minutes... got a negative that looks to the naked eye like it might be tough to print in a reasonable time but which actually printed very quickly, with good tone. i don't have it scanned or I'd post it.
The drum did get a bit smelly, but I rinsed it out well and let it air. No harm done. Caffenol stinks. No two ways around it. I just ground up the beans jnanian roasted up (in his electric frying pan!) when I went to see him last week, and I'm cold-brewing them for more developer. I soak the grinds in cold water for 24 hours and then filter well. With good coffee, I do the same but for 12 hours. It makes a very nice coffee concentrate that I use for iced coffee.