A customer sent me this which I made using a stainless steel set screw for the 1/4-20 stud. I tapped aluminum hex material with 3/8-24 on one end and the 1/4-20 on the other. The 1/4 inch set screw locked in the threads to leave enough sticking out.
Heavy Duty Antenna Mounts for Mobile Ham Radios $10 Flat rate Shipping with Satisfaction Guaranteed !
A custom piece to fit the tire rack. 4 X 4 aluminum angle with a thick plate bolted in with a 3/4 inch center hole. The two mounting bolts for the bracket are 16 inches apart and attached to a rack as shown to the right.
A trailer hitch mounting bracket for the big ones. Custom made to any height you might need. This one is 30 inches tall. The 2 inch square aluminum in the receiver is a solid bar and can be any length you might need,. This one extends 11 inches from the normal pin hole. Locked in place with a 5/8 inch bolt instead of a pin to be tight and not rattle.
Whatever your set up, we can make it fit.