Even if it does not go off like a fire-cracker, you should still hear it if it has happened. I dont use a HG so I have no first-hand knowledge to assist, however, depending on the volume you should be at FC within 10 minutes. A risk in getting there too slowly is you bake the beans and turn them into useless rocks. Something you might consider is pushing it hard (hot and close) and take the roast right through to black and oily and see what you must do to get there while noting how long it takes. You then back off with subsequent roasts until you get to SC in say 12min to 16 min (depending on volume). Citrus/acidic characters means the roast is too short. Dark and acidic could mean too quick and point to the exterior cooking faster than the inside.
You should get a good response from other HG gurus here. Rich has a lot of experience with HG roasting.