UA flies into B if I recall into the non-schengen, and FLR would be schengen, so most likely you would be going to Terminal A. Can you make it in a hr? I did. You would pass again through security, but there is an elite line too which as a *G I was able to use.
Question is, do you really want to? Europe C is not impressive by USA standards. The seats are basically the same as E with no extra legroom or recline. The only diff I noticed is you get a nice meal and better treatment. But even on my short hops from MUC-KRK in E on LH, I still got a sandwich, free drinks (incl booze) and tea/coffee with refills, so it really depends. I would just enjoy the RCC arrivals and relax after a long flight.