I'm about fed up trying to put up a decent number with daily tuning. Next idea since I can't fit 15s and a single 18 might not work.
Single 6 inch flared aero, tuned at 34, 17 inches total. Box will be 3.2 net after port subs and bracing. Subs up in the back corners, port firing out the back in the center about 8 inches from the back of the car.
Opinion? I'll post a pic of the current box in a minute. It's 3 cubes net tuned at 31hz. 54sq inches of port, 18 per cube. It did a 145 sealed up at 46hz.