Luis...
Here's another idea regarding photographing BIF. I did this when my long lens was the Canon EF 400mm f/5.6L which did not have image stabilization...
Cement one 90 degree curved conduit to a length of straight conduit. This will be be one hand grip. Determine how long you need the straight conduit so that it is comfortable to hold with back of straight piece at shoulder. Attach 45 degree conduit curve to the rear of straight conduit. This will fit over the shoulder.
You will now have one side of your shoulder pod. fabricate the second side.
Use a flat piece of 1/4" aluminum stock anywhere from 4" to 6" wide for camera support. The length of this camera support is determined by your size. Make it comfortable to hold.
Determine where the camera is comfortable to view and secure each end of the camera platform to one of the conduit shoulder pod sides with the hex bolts and cap nuts. I have skewed my camera to the left since I sight with my left eye. Position is determined entirely by your desires.
Attach adhesive backed cork to platform and mark the location of the tripod screw.
Drill a 1/4" hole to mount the lens tripod ring. Determine exactly where it is convenient for you to view the camera. Ensure that the camera body is placed far enough back so that it can be turned to vertical.
Mount the tripod ring using the thumbscrew and secure with the wing nut.
Cover the curved conduit with pipe insulation if you wish.
Secure a remote release to a front handle. I did this with a nylon tie. Although I am right handed; I chose to attach the remote trigger button to the left grip since the release socket is located on the left side of the camera and I did not want the wire to stretch across the platform.