You can report any problems with O2Hook2 and O2GraphicExt or make feature requests for them here.
Note that this is for reporting and discussing problems and feature requests for the mods, not a place to ask how to use them.
Any problems about the game client post-launch you encounter can be reported here. Anything that goes wrong before you start the game isn't relevant.
For feature requests, anything that is missing and you find particularly useful or fun could be added. I generally don't oppose much as long as it's a feature that many could find use in (it shouldn't solve some very specific problem likely only unique to yourself). However, feel free to ask anyway, as i might do something that personally interests me as a problem, even if it's realistically not something many people need.
Anything that you think i already know about, but that wasn't mentioned here yet, should still be created an issue for.