Dunno why everyone is saying "Don't touch the u2xmp.ini". Actually u can modify it all over but u have to be sure that those settings are all correct. I do use it to generate new custom u2xmp.ini files like myu2xmp.ini.
Included in u2xmp.ini are the default settings which will be used to generate your custom server file. Mine is a bit modified so it will generate the most settings I use on my server now so I havent to do it all again.
Well i started to use only the u2xmp.ini file since I got a backup of the default u2xmp.ini and the modified one I made and I only use 1 server. If something goes wrong I only have to copy/paste the file. Works perfect. Never had any problems.