Trouble Upload Product Options

[concession-supply.com]

We are trying to upload product options (additional options) via the import tool. This is not working for us. Is there a trick to uploading additional options to existing products? We assign the featureid featureprice sorting, etc, then Import the file and nothing happens!
Thanks in advance. :)

UPDATE: We figured it out! We were adding the featureid in sequence from the last used featureid. This must be left BLANK!