It is easy to get in the same boat as you are. I have been in the B group for at least two years now and in truth I am inbetween the A and B group in speed for 40 miles. The problem is I am more B group in climbing than anything else. If the climb is short enough I can hang on and draft till I get my breath back on the other side. But if it is a long grade I am toast. I have been lucky in that our A and B group tends to regroup at the same spots so if I can't hang I can simply wait till the B group get there and finish the ride.