My hat is off to anyone who tries, but...if you're seriously arguing with a guy who is either not quite bright enough to properly understand the concept of "circular argument," or not honest enough to properly apply it, you're wasting your time. If, OTOH, you're arguing with him only because it's as good a way for you to pass the time as it is for him, and you don't expect anything more from it than some entertainment, carry on; just don't lose the proper perspective.
For myself, I can only say that I've never seen a better example of the typical CTist "anti-consilience" approach. Yankee's entire premise, his "physical evidence," is a few photographs of the building and his personal, uninformed incredulity that an airplane could have done it- that's it, he has nothing else. And every other bit of evidence- eyewitnesses, video, actual physical evidence such as airplane parts and passenger DNA found in the wreckage, the absence of the airplanes and those passengers afterward, etc.,- is made to conform to that deliberately narrowed viewpoint; his "explanations" for all those things are nothing more than necessary rationalizations, handwaves at all evidence that contradicts one bit rather than examining the one bit in light of all the others. So, congratulations, yankee- you may not agree with your fellow CTists on the details, but you're exactly like them in your broad methodology.
One other thing- you are, in fact, making a positive claim- that the damage to the building is inconsistent with having been done by an airplane in a way that is testable by a simplistic, brute-force experiment involving running a wing into a mock-up of the building (which is a silly way to test the proposition, but we'll go with it for the sake of an entertaining argument). So, a couple of questions-
1) What parameters are you setting to establish whether or not the damage done in your test effectively reproduces that done on the actual building? What's the basis for comparison? Just that one bit of cladding? Will you claim that, if that's not replicated, the test is successful (from your POV)? Surely you at least understand that a chaotic event like flying a plane into a building can't be so exactly reproduced as to duplicate the same outcome twice? If a baseball player knocks a ball out of the park, nicking a light pole on the way out and then breaking a car's windshield in the parking lot- would you claim that no baseball could have done the damage to the pole or car on the basis that no test could exactly replicate the trajectory it took to do that damage?
2) Since you're making another positive claim- that it was missiles that did that damage- are you willing to test that the same way? Will you, at some point, test for what you say did do the damage as well as for what you say didn't, by putting a missile analog through the same building mock-up, with the same criteria that, if that cladding damage isn't exactly replicated, it shows that it couldn't have been a missile that did it? In fact, it seems to me that you would want to do this test first, since it would (by your standards) establish positively what you can only otherwise claim by a negative.