[TYPO3-english] Representation of Countries in fe_user?

[rsbrux]

In the Typo3 4.5 implementation I inherited, the country in the user's address (added through the sr_feuser_register extension) is represented in the DB's feuser table by the 3-character ISO code, cn_iso_3 from the table "static_countries" in the static_info_tables extension.
However, the country in the user's business address (added through the sg_feuser_additional_data extension) is represented in the feuser table by the uid from the static_countries table.  
The dropdown lists for the two fields look the same on the front end (presenting cn_short_en to the user), but obviously deliver different index values to the DB. 
I would prefer to have all country data represented in the DB by the 2-character ISO code, static_countries.cn_iso_2, but have spent countless hours in vain trying to figure out where this is wired up.
Would somebody please give me a clue?
How or where can I influence what the dropdown selector delivers for writing into the DB?

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Typo3 4.5.18 - 4.5.29
PHP 5.3
mySQL 5.5 x64
Windows 8 x64