Simple rigging question

Hi guys, I have a simple question that caused a lot of debate at work.

The question is this.
When you put two 2 legged bridals on one hook do you consider this a 4 legged bridal?

We were lifting 60 000 lbs with this set up. I argued that we should treat this as a 4 legged bridal situation and have each sling able to carry at least 30 000 lbs (half the load). The craine operator and supervisor both told me I was wrong and that we have to be set up so that each sling can at least carry 15 000 lbs (1/4 the load). So they were happy with each slings safe working load being 21 800 lbs. So I think its pretty simple and that they are both wrong. So please let me know if i am correct or if they are. Im going to take this further when i get back to work so that our procedures can be changed and we will all be working in a safer environment.
Thanks for your time!
cheers

This forum is for rigging related to computer graphics, not crane operation. Sorry we can’t be of help.