ok, so I´m now finally in Brazil. Thanks for all the tips and comments. In the end I transited thru ORD, or rather sailed thru ORD. It was a breeze. Was out in thirty minutes. Actually the immigration officer immediately recognized my non rev ticket and made a joke of my itinerary. Very polite and efficient. All the counters were manned.I opted at the last minute (again) as the FRA IAD was suddenly booked solid. Getting on the UA to GRU was also easy pickings. This was my first time at ORD (was there more than 20 years ago as a child so that doesn´t count)but I´m quite impressed with it. Especially terminal one. Great combination of style and function. And very easy to navigate. The eight hours I had between flights passed quite fast (but thats perhaps me, I like airports)So let me get back to my capairinha. Best regards