I agree wholeheartedly with your findings with timings against the size of the roast. *I only started roasting 2 days ago and my first batch was raw. *:-X
I figured after the first attempt that I shouldnt be a chicken and push on into second crack - which after reaching once and knowing what to expect is much easier now.
I find that smoke really builds as you start to hit second crack and then almost pours out as it starts to roll, but dont necessarily need to stop there. *I have found that I get the colour and taste that I was expecting at 15 seconds past "rolling" 2nd crack. (I back off with the HG as the smoke builds and coax the last bit of the roast)
Once this is done I drop my colander into a bucket with a vaccuum attached to the bottom and whisk for around 30 seconds at which time the beans are cool enough for me to put my hand into.
Im going to try and move my operation further down the yard though - the smoke is fairly invasive and the chaff is pretty messy too :)
I also found that bringing the beans inside too early also brings the smoky smell in. *Im now leaving the beans outside for a couple of hours to air and then leave them until the following day to make my coffee.