I would;
a) Use them with the backing plates - though I would use somewhat larger backing plates if material was available and I had the tools.
I would make them as long as possible in the up/down direction, wouldn't worry that much about the left/right direction.
b) Mount them as close to in line with the bucket cylinders as practical.
c) Use the biggest anchor shackles (probably 3/4 inch) that I could fit in them.
d) Step down to 3/8 chain hooks, perhaps via a smaller anchor shackle.
This is one of the nice things about NOT having welded on chain hooks, you can go to any/every size chain hook via anchor shackles.
I switch between 3/8 and 1/4 inch chain a lot and it is HANDY to put 1/4 inch chain in a hook and not have it jam because the hook is too big.