I used two #2 ground straps off of the battery in my Duster, one went to the stock hole in the wheelwell flange on the passenger side and the other went to one of the bolts Thumper is using I have drilled through the trunk floor through the sub frame flanged with one ground strap and had issues with the starter laboring on the hit when the motor was warm, ended up melting the battery post lugs and the lead clamps on the cables I do use multiple grounds off of the block to the front sub frames also