If he wants a shot with it staying at 40lbs then yes he can hand hold it but taking a shot with it reaching up there he’ll need a mount.
As for the camera not hunting for AF there is a possibility it could hunt. I had that problem when I was trying to do my interior car shots and I was trying to get my camera to focus on my lit headunit. Granted my setup was just a tripod set up in my hatch. It took up the whole hatch being spread out but under a load your going to get vibrations movement. A constant speed I was fine but didn’t get the nice trail on the speedo and tach.
These are raw shots. These were just tests for a contest.
I drove thru a sprinkler that was pointed at the street on this one.