Settling Transportation Charges on TCM to ECC: no negative charges allowed

The background: It's pretty common for a freight cost calculation to include both positive and negative amounts. Start with, say, the base freight charge for $100, and then, say, a negotiated carrier discount for that freight rate of 20%. The discount, of course, shows up as a negative $20 on the charge calculation for a net charge of $80.

TCM works great here. The problem is settling this freight order (really the freight settlement document FSD) to ECC. Once I hit the Save and Transfer button on the FSD the resulting ECC log (sxi_monitor) records an error referring to the negative (discount) amount.

I know that there is a fundamental limitation in ECC for posting negative amounts on freight service PO's (really a negative amount on the Service Entry Sheet). I suspect that this is the problem I am running into.

If I take a different Freight order / FSD and deactivate or mark the discount line as statistical (either way works) the FSD posts to ECC just fine. Of course the discount is missed and ECC overpays the carrier here ($100 instead of $80) so this is hardly an acceptable workaround...

Now my question: this is a huge functionality gap for TM! In my experience it is very common for freight charge calculations to include negative components. In a Marine environment for example not only are there charges and discounts but native calcuations that could be positive or negative (bunker adjustment charges, despatch / demurrage charges) depending on the situation. Has anyone identified any workarounds for this problem?

I have a couple of screen shots available in a Word document if anyone wants to take a look - I don't see a way to attach a document to this posting.

Thanks in advance!

Mac McLarin