I've tried extending and shortening our trip by one day on the outbound and return. No luck there. I've also called back once to have someone check again without result. The international desk told me that with only one flight per day, the available upgrades and award seats disappear quickly.
As someone else noted, regular Envoy award seats are very difficult to come by. For shoulder and in-season travel, you have to book them 330 days out.
I'm NOT going to burn 320K miles to ride up front. I'd rather drive to BOS and pay for a $500 W class seat and ride in coach. Then I could save my miles for Star Alliance awards.
At this point, I'm going to keep watching and calling. Perhaps something will open up. It's interesting to note how US' philosophy on trans-Atlantic pricing has changed. Last year, upgradeable fares were often less then non-upgradeable ones. Now, upgradeable fares carry a significant premium. A smart move for US, but hard on my checking account. I also wonder how the upgrade situation will be later this year and early next year when only CP's will upgrade certificates for these routes.