I think I understand your requirement, sometimes our other customers also have these requirement, but all the risks will be afforded by customers themselves.
We have two questions:
1st, why do you need new sales contract? You can totally issue L/C as per our real sales contract, and we provide real documents to your bank to collect the payment, the requested documents for custom clearance, we can send to you by DHL separately.
2nd, To use different documents to do custom clearance, is there any risk? Is there any possibility to influence us to collect the payment? As we know, last shipment, before you pay the L/C, you have already taken the pipes to your warehouse, I think you also have finished the custom clearance before paying.