Re: the 18 minute roast on the SR500. It was one of the better batches I'd done; however, taking these Columbians to FC++ is not my preference. I could still taste some English walnut, but it was pretty much eclipsed by a kind of thin carbon taste. Not awful, but not great either.
Tried again today. 2 minute L heat, high fan (using the SM shake method); 1 minute H heat, high fan; every minute after I took the fan down a 1/4 notch until almost L fan. Hit first crack between 4-7 minutes. Stopped it just before 2nd crack.
The good news for me, is now I can see progression and have a baseline for experimenting. I'm sure other people's mileage will vary.