Get the king size mattress and build it around that I built mine around a queen size mattress. Don't be thinking about putting it in and out though. Put it in there and leave it there. you can get it in as long and the door is big enough and nothing beats a home style inner spring mattress. I just put my full size inner sprint mattress in my teardrop. I know I modeled it around a queen but I just replaced my home mattress and I still had the decent full size around. Just shove it in there...
I think there would be NO claustrophobic issues with a teardrop that big, mine feels huge. ALOT of people say that who have never actually been in one. like what was said you guys need to go to a teardrop gathering and actually sit in one. Totally different world.