Truthfully I have no idea which module should get this issue. I created this issue (http://drupal.org/node/798570) to figure out how to set the initial group on a node add, so that the proper vocabularies would show when creating new content. That worked.

Next I tried to add a custom node add page to a group panel.

I did this by following the general recipe found here: http://drupal.org/node/553456#comment-2555614.

Basically, you create a new panels page, set the access control and selection rules to your group content type, make the menu settings a 'tab', and use the 'organic group from node' relationship context. Then I can add whatever I want to my panel layout, like a view or whatever, and I get that panel tab on each of my groups of the same type (I have to send the arguments to the view, of course). Works brilliantly.

For putting a node add form on a group panel, I did the same procedure, but I additionally added the 'node add form' context. This allowed me to select the node add forms for the panel content.

Voila! The panel tab does show up on each of my groups, and the add node form that I want does also appear on that tab.

Remarkably, even the proper vocabs for that node add form are displayed, exactly as I wanted.

But there is a problem. For some reason, even though the form must be getting the proper context, because it is only showing the proper vocabs for the OG group that I am adding my node to, it _does not_ actually select any group in the node/add group section.

so, I get the vocabs listed (as if I had sent ?gids[]=xx), but there is no selected group.

Is this a bug?