Alter Organic Groups membership requests

I want to remove the option "Invite Only" from Membership Requests in Organic Groups.

I've tried to do a hook_form_alter but I've had not luck.

Can anyone point me i开发者_Python百科n the right direction?

Using: Drupal 6.16 Organic Groups 2.1

I've done some work on modifying/simplifying Organic Groups - here's the code on GitHub: http://github.com/voxpelli/drupal-og-enhanced/blob/master/og_simplemembership/og_simplemembership.module

Hopefully that helps a bit - there's some other modifications as well in the other modules in that repository - all open source of course :)