If you have a 2.5 inch thick pad such as a thermarest xlite there is no way you will fit at 7′.
I would say somewhere between 6’4″ – 6’6″ is probably the maximum. If you had a thinner foam pad it would be doable higher. It also depends on what kind of sleeper you are. If you like to spread out you might have to adjust the way you sleep. If you sleep in the fetal position you could get away with being taller.
For reference I am 6’2″ and its a pretty close fit give or take a couple of inches. Personally I think even an inch less room would be quite annoying for me because I like to spread out a bit, and I already rub the bottom of the tent with my sleeping bag which results in a damp bag when there is condensation. I wish there was more room for me. However I adjusted to the amount of room I have pretty quickly so its hard for me to say how much less room I could take.
You will also need some way to keep the pad from slipping in the tent. There isnt much margin for error as to where you can put your pad. I use a thinlite pad under my Xlite and it does the job very well. It also has a host of other uses which is why I bring it. Apparently you can also use seam sealant but I have not tried that.
I will say that its an absolutely amazing shelter. It’s very reliable and easy to set up and can handle storms surprisingly well when pitched low to the ground. I haven’t had any issues so far durability wise after about 30 nights. The fact that you get full bug netting and a reliable, quick set up that can fit a tall person for just slightly more weight than a skimpy tarp and bivy set up is pretty amazing.