What are the floor dimensions?
The website I found gives 16.8 feet squared. As you can imagine it is narrower (and lower) at the feet and wider at the head. I am 5 ft tall. I camped for a week in this tent and thought it was plenty roomy. The head area is high. I even had my pack in the tent and used it as a back rest when I wanted to sit up and read, etc.
I agree with Elizabeth's dimensions. I measured 85" long and just over 37" wide at the shoulders. I am 6'3" and fit in the tent without problem with a cold weather sleeping bag. I don't think you could use a large rectangular sleeping pad in this tent, but a tapered pad works great. The tent provides a lot more room and comfort than a bivy with hardly any extra weight.
I made three measurements. The length is about 85 inches. At the narrow end, I measured about 20 inches. At the wide end, 39 inches. I am 5' 2" and found the tent plenty roomy.
I have to say that I bought this tent for a friend so it is at her house. I will email her and ask her to measure the floor for you, but I would not hold my breath for a reply.. She is a teacher and very busy. That being said, I will tell you that I have seen this tent set up. The foot end is thinner the the head end- shaped like a mummy bag. You could probably fit one of the new mummy bag shaped pads and sleeping bags inside nicely and fill the entire floor space. we just hiked the Grand Canyon and she got it for that trip- free standing, air ventilation, weight and she loved it! This hiker is also 5'5" and about 120 pounds soaking wet. I will forward this message to her and if she has time, you will get a 2nd reply.