I have an Tepui Autana Ruggedized and I keep 3 Kifaru sleeping bags inside, 2 20* bags and a 0* bag. I also keep a Hill people gear Serape, I have used the serape as a bag down to 30* just fine. If its colder than that I know can crawl into the 20*, my daughter is a polar bear like me so she is fine in a 20*, the girlfriend is NOT even at 60* she will be in a 0* bag. I also keep the pillow up in mine, they are the exped pilows. Down filled with air bladders, comfy for camp pillows, when deflated they take up no room at all, there are 3 of them up there as well. In the Raingler ceiling net I keep another Serape, and 2 Kifaru Woobies. I know we are good for just about anything they would ever want to go out in regardless of how bad it gets.
As for the bags, I found that if I fold them in half where the mattress fold, and since they are mummy bags, if I keep the fold about 25* down the center, the feet and hood just barley nestle together creating a smaller package. Then I fold the serape just neat the middle. The frame and floor allow it to compress easier. The Autana is similar to the Mt Shasta in size and construction.
I have the annex and the floor if needed and on long trips take it, but personally I hate them. Ill take just the tent any day of the week.