Costing of items with Dual UOM

Hi,

Is there any documentation on how costing and Mfg accounting works when an item is in dual UOM?

For Ex: Item 1 UOM1=CS and UOM2=LB there is a UOM conversion on the item level. EX=: 1 CS= 10 LB

Costing is based on the primary UOM.

when a WO is created for 10 CS (UORG) and 100 LB (SQOR)

inventory completions is done:

#1: 1 CS =10.5 LB

#2: 1 CS=10.75 LB

#3: 1 CS=9.75 LB etc

How does mfg accounting accommodate the difference in weight completed in the variances?

Thanks for your help