Trying to settle an argument (AUS)

I don’t want to post photos due to privacy but I do have a sketch if I need to post to clear anything up.

So we have a 47XXton Chute wing wall lift.

Two over head cranes 15T each

2x 5T chains 2 legs

One side is lifting shackles and chains to hook,fine with that not a problem at all.

Second side is my issue and I’m not being heard about it.

Side 2 is 2x2.5T lifting lugs.

(Before we go further just know these lugs are less then 20-30mm through the nut,you can still see a thread or two on said nuts red flag🚩)

Supervisor is arguing 2.5x2 =5T.

My argument is we round the load up for safety and say it’s 4.8T

2 lugs at 2.5T best case we are at 5T but that’s 96% capacity, so any load shifts or one leg takes more load then the other = fail

Lifting angle I’m seeing will be around 30-50* so -85%

5T x 0.85 = 4.2/4.25T so we would be roughly 500/550kg under anyway

Now have I messed up in my thinking/maths or?