Load securement using shackles

This is a good question. I do not have the answer.

 

I wouldn't see why not, your not exceeding the Working Load Limit.
But, that being said, a DOT Official may want to argue the point. I've seen Canadian Officials, make drivers replace straps merely for having the WLL tag that is stitched into the strap being missing.
As far as I can see, if it's rigged right, there shouldn't be a problem

 

I'm sure the DOT can find a problem with it.

 

I’ve used 10 ton clevises with 2 point securement for years. Never had an issue with DOT.

 

Here is a chart from Crosby on side loading a shackle and how to caculate the reduced WLL depending on the angle your attaching to it from. It should apply to your question as well since when using two pieces of securement on one shackle you will be side loading the shackle somewhat. Hope this helps.

 

I prefer actual Crosby shackles though. With Crosby there is no question you are good. The Chinese shackles leave alot to be desired. We have had a few distort and had trouble getting the pins out.