PabloACZ has created an app that will switch the IOS that NeoGamma uses.
download - NeoGamma IOS SwitcherQuote:
I made a quick tool (with the help of some friends) to change the IOS value on the NeoGamma.cfg file, so you don't need to hex edit it. It's useful for noobs.
It allows you to switch the IOS to be used to these ones:
* 249 (which comes by default, so there's no need to set it).
Just choose the one you need and press A to apply the changes.
Anyway, here's it: NeoGamma IOS Switcher. I'll leave the fancy icons to you, ppl; I even suck at Paint.
source - gbatemp
I have tested this and it works good.
Download and extract. Copy the NeoGamma IOS Switcher folder to the apps folder of your Wii SD card. Run from Homebrew Channel. Thanks to JoostinOnline for the meta file.