The light roast for cupping (when used as part of a sample roasting protocol; it's important to distinguish between this and other uses of cupping methods in training, product development, and QA functions) isn't about maximizing the bean's natural flavors. That's a common myth. Rather, it's about not masking defects and getting enough information about potential flavors to make smart buying decisions. In truth, as you roast a coffee darker, you're going to diminish some flavors while further developing others and the decision that you make about where to end the roast comes down to the specific flavor results you want to achieve, which should vary depending on the coffee and on the preferences of the person who will end up drinking it.

If memory serves, you should have a large enough trier that for full batches you should be able to pull a bunch of samples (enough to get 1 cupping bowl each, you'll probably need a few trier fulls and it takes some practice to get the coordination down) during a single roast and thus get the full range from very light to very dark to taste. That's the fastest way to gain sensory experience with new coffees. Only after you've decided on roughly where your degree of roast should end up should you worry much about the timing of how you get there. In other words, the decision on degree of roast is going to be responsible for the vast majority of the differences in flavors you can get out of the coffee and the timing of how you get there, while still tasteable, is responsible for substantially less of the potential flavor variation.

In the case of coffee from Sulawesi, these are often quite boring at light or medium roasts, but you push them out to around a 30 on the Agtron Gourmet scale (substantially beyond SC) and they can develop neat sweet spice flavors along with a good thick body.

The cool air thing can be an issue on some machines, especially on smaller machines, but at 1Kg and larger that concern is often overstated. Especially if you can back off on the airflow, it's often not the big deal you might expect (small inlet hopefully outside of the primary airflow, covered by a much larger flowing mass of coffee, you can use a strip of paper or a lighter to get a rough sense of how much air movement we're really talking about on your specific machine and if it's a recent enough MCR you might have a gauge and fine control over that). Given the value of the exercise, I wouldn't preemptively discourage someone from trying and making that determination for themselves.

The video yakster mentions is probably this one: https://video.typica.us/videos/watch/a4 ... a78155139b and the technique is also used in the Roast Profile Development videos at: https://video.typica.us/video-channels/ ... ing/videos (Disclosure, I'm the same Neal/N3Roaster who made those and the videos are also available and easy to find on YouTube if you'd rather watch them with ads)

It's very easy to imagine theoretical reasons why an exercise like what I've described won't work (and different ones every time this topic comes up!), but have those who are objecting actually tried doing the exercise as shown and did you not get a sense for how the coffee used changes as it progresses from a lighter to a darker roast? I never see the objection, "I tried it and because of factors x, y, z that I couldn't figure out how to mitigate I couldn't learn from the experience." That's kind of the point here: to get a good overview of what the general ballpark potentials are for a coffee you're not familiar with, and to explicitly try things that might be outside of your usual comfort zone. It's not the thing that you'd do for your day to day roasting once you've figured out where you want to take that coffee, it's probably not the best use of coffee for the typical home roaster operating under the constraints of not having a ton of the same coffee (and I'll admit that a lot of home roasting equipment in use doesn't make this practical which in no way says they're not making delicious coffee, though plenty of people here do have machines large enough to try this, including the person who first asked the question), and it's not even the last step in a product development process, but this is an exercise that I've repeated both in classes I've taught and as a starting point for product development on (back of envelope estimating) a few thousand different lots of coffee over the decades on a variety of machines (though mostly split between a couple of Diedrich roasters in my shop, a 1Kg and a 12Kg). I can only speak to my own experience here, but this has never failed to be an informative exercise for those involved.

As an aside, clearly a trier you can't use is indicative of a design flaw rather than not having a problem using the trier indicative of operator error?