You mentioned elsewhere on the board that you do group orders from WGC.
Having an SD6, I would take a look at batteries that are specific for your model such as
http://www.wgcshop.com/pcart/shopper...281a6f60581590
It may have a higher voltage than the 8.4v but the 1500 mah will keep the ROF sane.
Think of it as a comprimise between the 2 batteries you had chosen.