Drill and tap a 1/2 in hole in receiver, then tape that hole.Next screw a long threaded bolt with a nut on it into the tapped hole,run nut brown to side of receiver FINGER tight.Weld that nut to the recieiver.That gives you more threads because receiver is to thin and soft to hold.I did this with two on one side and two on bottom.I also made shims for top and side.I also made shims for every place a bolt went thru on the ball platform.I used grade 8 bolts.After a few trips I will add a little metal where the bolts wear.(after a trip to Yellerstone from Ga,or a trip to Brownsville Tx)I have my welder and torch.