With the help of fohat.digs, I have discovered that Model F AT feet are not interchangeable with XT feet. Probably some people already know this, but I couldn't find any information on the subject when I was looking for it so if that information is already out there it's hard to find
Anyway, here are some pictures to illustrate the foot difference. Not pictured are the spring mechanisms for each foot, which are also different between the AT and the XT.
AT
XT
Potato pics yes but you get the idea. Hopefully this helps someone else! And also, someone sell/trade me a Model F AT foot