When I designed this method - the welding was not a consideration that I was worried about - 1/2" plate with grade 3/8" grade 8 bolts. The plate was beveled and triple passed by someone that does a lot better job than the bubble-gumming that I might have done!
This method was created to pull in a direct line with the dipper arm and boom. Someone a while back made a comment on pulling side to side, the damage to the bucket,stick, and boom would be my biggest concern. I have a large tree that fell close to a creek line, the hook allowed me to pull the tree closer, and then lift smaller sections of the tree up and over the bank of the creek.
I used it a couple of times and it worked well - but I have not used it in about 2 years till the other day - wrapped some chains around a MMM and could pick it up and place it on a trailer. It is nice to have a pick point there much like the FEL.
Like Kenny's hooks - I would rather weld to a plate, then bolt, due to the ability to take off and modify or change. Also - depending where you weld - you do create a weak spot on the piece of metal.
If I did not have an AG shop next door - I might have gone a different route.
I made a mock up of the entire thing from wood! and then took the wood over and explained what I wanted - those kids (they have a great teacher too) do some of the finest welding you have ever seen - its like a game to them, who's beads look better.
here is a better picture:
