I didnt add any angle to mine as I dont believe in putting a hook in the center. If I want a center lift, I just hook my chain in both side hooks and then back into the chain centering it it a Y at the center. Most of my lifts are with the chain running across the bucket and down to attachment point at each end.
As for attachment, I welded all around the 3x5 plate then plug welded each of the 4 holes that were in the plate so it is welded to the FEL in the middle of the repad also. Remember that for repad, I used a mounting plate for attaching load springs to an axle so it had 4 holes in it for U-bolt. This added extra strength to the attachment point although not really needed for strength, it does keep water from getting under the plate which could cause corrosion or freeze which could buckle the plate. If I were putting on a reinforcing bar of some sort, I would do like OLDTOYBOYD and weld the ends solid then stitchweld about 2" of weld on 12" centers on both sides of the bar with the stitches alternating so you have a weld every 6" but on opposite side. The fillet weld size should be the thickness of the material that you are putting on, i.e. 3x3x 1/4" angle would have a 1/4" fillet weld at least 2" long but not more than 3". Too much welding will cause some warpage on your bucket.