How to chain excavator buckets without the excavator?

I'm very new to working with flatbed equipment and I had to drop off the excavator but keep three buckets.
They're nested inside each other, from smallest to biggest, and I wasn't sure how to chain them the safest, because they're so small compared to the trailer.
I threw two chains over them kind of in an X shaped and put the chain through the tops.
After one stop to tighten they seem secure but I'm in a learn as you go type situation.
Could I ask if there's a better way to secure them?

 

The trailer is dropped off at the yard for the weekend. First time in 5 years I've done any kind of local stuff. I kept forgetting my car keys in the work truck the first couple weeks.
Life is strange without the home on wheels.

 

Thanks! I'll add some 2x4s to keep them from rocking and I've got the chains through the attachment points, through the tops.
Everything seemed so sensible when the equipment has little spots to add a chain!
Take away the actual equipment being hauled and I realized I had a lot to learn!