We crossed to Riding Rock in a 30-footer many years ago and it was a great trip. We left Rodriquez about 5 AM and did the 75 miles in about 12 hours, with a good help from the Gulf Stream. Also it was blowing like stink from the North (not recommended) so we were moving pretty good. It was so rough that the Coast Guard swooped down in the helicopter and checked on us at one point--it turned out they were looking for someone who sunk in about our position. Anchored at S. Riding Rock (rolly) over night before heading up to the Northwest Channel the next day, which I believe is about 56 miles across the banks.