put a case or 2 of paper in the trunk should help!
last winter, I cut a round piece of plywood the the inside size of the rim of the spare tire, i put body side molding around the edge and felt on the top. got a 50lb round barbell weight and placed it on top of the plywood. Also drilled a hole through the plywood. Then I got a long bolt to replace the holddown bolt, a flat washer (with a battery post washer - felt), and secured it to the spare tire hold down.
drove all around without issue after in the NJ snow last winter (which was plenty). the hold down kept the weight from shifting during turns/breaking.
hope it helps someone, cant wait for the snow!