Chim - I didn't realize you don't have the QA bucket. I think I got some versatility with my setup (maybe not as much as yours). I got the clevis mounted to the center of my bucket, but have yet to weld the hooks on.
Right now I have 1/2" grade 8 hardware with two washers beneath the bucket. The bend in the plate should add some strength to the bucket as its only 1/4" thick. The actual clevis mount is welded to one of Ken's Bolt on Plates that's 1/4" as well. Because of the lack of support beneath the bucket for this one mount, I'm not expecting it to pick up a huge amount. It may, but I'll be cognizant about bending the bucket.
As for the heavy lifting, the hooks in line with the hydraulic cylinders should do the trick. Again, I intend to weld the hooks directly to the buckets 1/4" plating, but beneath it is a long seam weld that's used for the QA assembly. I don't foresee that area bending much if at all.