Maybe you a little misunderstood my meaning, actually the amount on FORM E and on invoice can be differnt, we can make them different to satisfy your requirement.
The most important for us is to make the amount on FORM E to be same as we declare to customs, for example, if we receive payment 10USD from abroad, we have to declare to customs 10USD, then we show 10USD on the FORM E, all amount must be coincident, but we don;t remind how much you put for the machines, and how much for spare parts.
How about do by this way:
after we make the PI of genuine unit price of machine and spare parts for you, you could adjust the higher unit price for the machines, lower amount for spare parts, as long as the total amount is same . Then after shipment, we declare the price to customs same as your false PI.