the round stock...
..inside the box tubing is a piece of heavy wall pipe that prevents the box tubing from crushing when the knob it tightened. I welded them in place to keep from losing them when I swap the position of the swing arm.
I used a 3/8" carriage bolt that sits in a square hole. I didn't want the stud to be permanant as the swing arm may need to be below the stationary arm to get low enough. The swing arm has square holes on each side so I can flip it around.
If I want it to go really low, I'll flip the swing arm so the square tubing that holds the grill post is down, and put the swing arm below the stationary arm. this position will put the grill about 16" off the ground when parked on level ground.
to go high as possible the swing arm is on top of the stationary arm with the square tubing facing up. The sky is the limit on how high I can go by changing the threaded tubing.
The length of the grill post (threaded aluminum tubing) is arbitrary. I just didn't want to cut it yet until I get more use in different camping situations. Then I'll shorten it if need be. the higher the post, the more wobbly the grill. Although it won't interfere with the use of the grill, I just feel better if it doesn't wobble at all. thus my need to keep the upper arm adjustable.
I camp in fields/parks/woods where the rear bumper of the camper may be 2+ feet off the ground-this puts the a-frame hitch on the ground. Sometimes the bumper is as low as I can get the camper in order to get the thing level- placing the a-frame hitch 3 feet in the air. for reference sake, the front hitch is about 20" above the ground when on level ground. I want to camp where I want to, sometimes in a campground. I never know where I may go next thus want to be flexible.