Neither of these adversaries can afford a technical attack. The guy at the airport will say "oh well", format the disk, and eBay it. The government will try to convince me that I do know the key, will fail, and will have to support its (theoretical, of course) case against me with actual evidence instead.
There is one thing I just thought of, though; the SMART log shows how much activity the disk has experienced. It should be easy to check this log to see which disk I use the most. I will come up with some way to plug this leak :)
But anyway, I am not sure this would "prove beyond a reasonable doubt" that I know the key. If any case against me ever depended on me decrypting my disk, I would first refuse. Then, theoretically, a charge of obstruction of justice would be filed against me, and the government would have to prove that before they could even consider their original case. (And that's no cakewalk, as there is case law saying I don't have to give up the password, and I don't think SMART data has ever been used in court.)
So anyway, I think my system is good enough. I don't have any friends in the government feeding me classified information, anyway :( So, it's likely that I will never get to test my system. But I hope the "Real Criminals" read this and perhaps use this information to help themselves stay safe from their oppressive regime.
The crazy thing about the TSA: I flew back from SFO to London last month. I had three laptops in my carry-on bag. I also had a can of Red Bull. Apparently, the can of Red Bull is highly suspicious, but the three laptops are not. I had a perfect excuse though: one was running OS X, another was running Linux and the last was running XP.
Customs is another story; they would probably ask about your laptops.