I am in the same boat. Ran a 1:10 in November and was planning on running fast spring marathon but injuries got in the way. I'm running a full in 2 weeks, but plan on running just fast enough to be in the first corral. It's been frustrating to know I HAVE to run a full now vs the fall to get a qualifier. I could also run just under 3:10 for the BQ then improve my time with a better fall marathon, but that would mean 3 fulls within 11 months. Not ideal.
2015 cut-off for 1st corral was 2:47ish. 2015 was 2:45 high, and I was number in the 800s with a 2:44 qualifier.
I think that if you are under a certain time at Boston, you should gain entry for the next 2 years, maybe under 2:40. That would put you in the top 150-200 overall in most years.