NEC3 Supply Contract Fee on Fee

Within NEC3 Supply Contract, how does the fee percentage work? We are looking at a supply contract that is to manufacture parts, some of this we will Subcontract. As there is only one fee percentage in a Supply contract for OH&P can both the Subcontractor and us charge their OH&P? The defined cost is the amounts paid whether Subcontracted or not, meaning if we subcontract then we will be paying their defined cost + OHP therefore can we apply our OHP to the Subcontractors cost? Supply Contract doesn’t seem to be the correct method of contracting but that’s for the Purchaser to decide I suppose.