Making padded arm rail is much easier than you think.
You start with a base plate in the desired shape of your arm rail.
The base plate is made from 3/4″ plywood and can be rounded or straight.
6 to 8 inched is a nice width to use, but you can make it virtually any size.
Once you’ve cut the plates, decide whether you want it mounted on the bar or gapped away from the bar.
Both methods will obviously add to you overall overhang.
The gapped method will require a simple mounting bracket. These are commonly made with steel rod
or even schedule 40 1/2″ black pipe like that you would use for gas lines.
Mounting directly on the bar requires just a simple 45 degree mounting block.
The next step is to cover your base plate with 3/4 or 1″ medium density foam.
This can be found at most fabric stores. While you’re there, ask about fabric backed imitation leather or Naugahyde.
Cover with foam first, then over with the leather, vinyl or Naugahyde fabric.
Use an air stapler with 1/2 staples to fasten the foam and fabric.