It's easy to go FP early in Boston
I got FP notice with appointment in August. But I just went to Boston office in early July without appointment. They let me do it. It was really easy.
Actually I went there early in the day. They told me to wait until they process that day's appointments. Then around 12noon, the line was clear so I was called. Since the office open until 3pm and on Saturdays, too, you can just go there after lunch and get it done!