Stormcrow was very helpful. He contacted me on his own within a few hours of my posting this! I definitely didn't mean to come across as unhappy with the Incubator. I have been able to make the Incubator cover the correct areas by holding it in place, so it is certainly large enough. My problem has been in getting it to stay where I want it overnight with the stock suspension. That suspension works perfectly btw on my ENO SN and still covers about 95% of the BB.
According to Stormcrow, there is a foot end and head end to the Incubator. The head end is slightly wider with the drawstrings fully loosened. Also, per his suggestion, I am also going to try looping a piece of shock cord with a cinch buckle over the ridgeline. To better keep the quilt where I need it, I will hook the shock cord to the right side (shelf side) of the Incubator near the foot end (looping over the foot box) and the left side (entrance side) near the head end, rather than just straight across the middle. I am confident that this set up will get me the results I want by pulling the Incubator into a slightly asymmetrical position. There has been a 3-day ice storm here in Conyers which has prevented me from getting out and testing this set up, but I will post back with the results as soon as I'm able.