Fedex rate calculation

I'm seeing a big difference between the Zoey calculated FedEx rate and the actual rate charged to me by FedEx on orders with large weights. I Have the FedEx Web Services information configured and it is providing me with shipping rates, however the price calculated for large order quantities is quite high.

For example: a customer orders 36 items each weighing 5 pounds for an order total weight of 180lbs. We ship the order in 6 packages weighing 30lbs each.

I have "Packages Request Type" set to "divide to equal weight" and have tried "use origin weight" as well which doesnt seem to make any difference. I'm wondering if Zoey assumes that all items will be sent in one package and because it exceeds the carrier maximum rate my negotiated rates are not applied.

Any suggestions for this scenario?

Thanks