Hi Tony, I run my heatgun on full speed initially inside the bucket approx 10cm from beans, it takes about 1.40 to reach 50C and then picks up pace, I then raise the gun gradually with 100C coming up around the 3-3.5min mark depending on beans I am roasting. I try and reach 1st crack around 12-13min mark and then 5-6 minutes from 1st to second crack. Watching the probe readout helps to control your application of heat, after several roasts you get to know the visual signs of smoke before 1st and 2nd crack and watching the colour of your beans at each stage. You want a constant ramp up of heat without stalling the roast.
Im sure after a few roasts you will get a feel for your setup and things will improve markedly............good luck and happy roasting!!