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.