Please tell me if it's possible (or necessary) to the Past Perfect Tense in the second part of the sentence (formal letter):
We would remind you that we (had) informed you in the pre-last shipment about the following...
And would it be better to use the Present Perfect Tense in the following sentences (as the result) and the definite article 'the' after 'a half of' (formal letter):
However, you (have) sent us only a half of the missing parts (wheels, nuts, screws) in the latest shipment.
No to the first question about the past perfect.
In the second part, you do need the article but you don't need "have".
"Invading armies have no rights." Noam Chomsky