This is what the PO of my trailer had done as far as a standoff. If I were to do it, I would not make it as tall as this one is and I would not put "ears" on the outside. When the antenna head was down, the aluminum wing on the AC side rested on one of the ears. It eventually cracked through one side of the aluminum wing and a crack was half way through the other. The standoff looks like a piece of aluminum bar bent so that the ears would keep the antenna arm reasonably centered or from swinging one side to the other. I would eliminate the ears and bend a small V in the center with rubber support of some type. I used a clear rubber bumper affixed to the antenna arm but you could use some type of rubber with screw to mount it on the arm. You could also use a piece of rubber in the V of the mount. Hope this helps.
'01 2500hd ext. cab, 8.1 litre gas, 5 sp. Allison auto
3.73 rear end
Mag-Hytec rear diff cover
Amsoil Dual by-pass oil filtration system
Amsoil synthetics all around
265 watt AM Solar, Inc. system