not very much of what follows is "approved", but it works for me. Just remember when you start playing games like this you need to pay very close attention near the end as you've possibly created situations where things, fire specifically, can go wrong. So be careful when you start operating outside the factory approved parameters.
Well, there are a couple of possibilities. First use P1, it's the hottest setting, most likely to reach second. Second, as soon as the roast starts hold down the + button till the max but you have to pay attention as you just made you responsible for pressing cool. If that's still not enough, then press P1, Start and wait for the clock to show 16:00, then press Stop, P1, Start and extend the time as before and this time stay closer. Not that the 2 minute pre-heat may cause a bit of smoking around 8 minutes, right before the afterburner turns on. Most machines will take a 2 minute pre-heat, somewhere between 2:15 and 3:00 you'll likely get it hot enough it will not re-start without colling it back down or fooling it with a ice cube to the temp sensor.
Some Behmors are slower than others, if you think yours might be to slow, call Behmor customer service and ask how to fix it, If you have a screwdriver and a minute or two the slowness with some of them can be cured.