Catch Weight

I am working on a project where catch weight was implemented badly (and need to fix it).
In my research, I have found 2 Navision add ons that say they handle catch weight - since it is marketing materials, there is not a lot of detail. The VerticalSoft (ColumbusIT) sounds like a good approach - dual units of measure - so you can buy cases, pay by the pound (kilos for those in the EU), and receive in both. Then have the capability to sell and ship the same way.
Has anyone on the forum worked in this environment where you have had to support cases and catch weight simultaneously?
Since everything is lot controlled, I am thinking the weight units could be controlled at the lot level, and adjusted at receipt or shipping time on the original purchase/sales order.