Sale order to invoice custom item field

[addady2]

It work for me in Sale order to invoice custom field but not in Sale order to invoice custom item field.

For example:
cf_1026 to cf_1031 (Sale order to invoice custom field) work
cf_10211 to cf_10671 (Sale order to invoice custom item field) work

Code:

<map>
  <originmodule>
    <originname>SalesOrder</originname>
  </originmodule>
  <targetmodule>
    <targetname>Invoice</targetname>
  </targetmodule>
  <fields>

   <field>
      <fieldname>cf_1031</fieldname>
      <Orgfields>
        <Orgfield>
          <OrgfieldName>cf_1026</OrgfieldName>
        </Orgfield>
      </Orgfields>
    </field>

   <field>
      <fieldname>cf_10671</fieldname>
      <Orgfields>
        <Orgfield>
          <OrgfieldName>cf_10211</OrgfieldName>
        </Orgfield>
      </Orgfields>
    </field>

  </fields>
</map>

BTW: why the ID of custom item field is 5 digit

Am I missing something?