I'd just add that there is some good anchoring at Block for a 22 foot boat. Just avoid where it's 50 feet deep and anchor where it 25 feet deep or less. You could try right along the boundry of the anchorage, along the north side of the anchorage (NE corner of the harbor) should be good.
Cuttyhunk is a personal favorite.
I'll second the statement about watching the tides. Also if you are going through Plum Gut or the Race, watch out for current against wind (waves get steeper) .
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