2 pounds of fresh/frozen blackberries in the secondary are the way to go. Put them in a bag and give them a week. The ABV will drop slightly.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk