I chose to use D rings also.
I used bolt on with a 2 hole strap. One on the top flange of the bucket another on the inside on both ends of the bucket.
I set them in right in front of where the curl cylinders attach to the bucket. The D rings are rated about 1700 lbs each. And when in line with the loader arms not putting too much undue stress on one side of the loader.
Besides they were on sale, and 4 D rings, and 4 mounting bolts, lock nuts and all ran about $30 Best match for my FEL size and capacity. This has worked well for me.
Your situation may be different.