I am not surprised that there is only 10% contact on many welded hooks. I welded many for lots of people over the years and I often get the request to only run a bead on the edges and leave the middle for a "witness" or just he opposite and weld the middle and leave the edges as a witness. Which only means to me that they are only making contact where the new weld is and using the old worn area to get it close. I could imagine that it is very difficult to get the orientation of the half round and achieve full contact all at the same time. One file stroke to much and you are screwed. As far as being able to tell if a hook has been welded it is nearly impossible if the weld has no flaws such as poor fusion line or undercutting.
