I'm planning a mileage run LHR-SFO-LHR, I'd land in SFO around 13.00 and the flight back is around 18.00.

What do I put on the green card as my temporary residency address for the 4 hours? What on earth will the immigration officer think of my trip? I had real hassle last time I flew into the USA, even though I was staying 4 weeks on vacation. They always seem to single me out...