There is no minimun mem said it all depends on what you have running at the same time, I did gained some good amount of MB by getting rid of most extra fonts, backgrounds, music sample, avatars so if you're bavre enough to try it go ahead...
You can get rid of all net_rim_mediOTA_xxxxxxxxx.cod files, just keep the one that says RINGTONES
Also all the net_rim_font_xxxxxx.cod just make sure you keep the net_rim_font_european_sff.cod and net_rim_font_latin_truetype.cod files,
You can also safely remove the tmobile_error_translator files this will give you around 12 to 15 MB more of available mem...
DISCLAIMER: try it at your own risk, I'm not responsible for the results you may get.
Posted via mobile device