Short roasts with SR800

I’m wondering how to get more complexity in my light-medium roasts. I’m getting to first crack pretty fast—5 minutes or so—and usually finish by 6-7 minutes. Results, mostly on Yirgacheffe beans, are ok but not great. Should I be finding a way to stretch the time a bit without getting to a darker roast? I’m doing 225 grams per batch, roasting outside in Florida, where it’s usually 80-90 degrees ambient.