Issue with preventDuplicates

Hi all,

Im using SmartClient version:
SNAPSHOT_v8.3d_2012-05-26/LGPL Deployment

I have the next scenario:
- One grid with products catalog (canAcceptDroppedRecords = false).
- One grid with Products to Order (canAcceptDroppedRecords = true).

Drag and drop enabled with dragDataAction: 'copy'.

If I drag one record from Products Catalog to Products to Order grid and if I modify this dropped record, if I try to drag and drop the same product again, the grid accepts it.

I think this is due to both records are not exactly equals in all their properties.

How can I prevent duplicate records just checking one property?
For example: Product SKU


Please help, this is delaying us.
Thanks in advance.