Attachment / Truck Capacity Calculation
CAUTION: Formulas can give you a good ballpark estimate of how capacity will be affected. 
But you should work closely with your truck manufacturer before making a decision. 
Their data reflects, in most cases, testing with specific trucks and attachments.
Maximum Lateral Offset while in the fully sideshifted position may dramatically affect residual capacity.
Check with your OEM lift truck manufacturer for actual capacity.