Multiple Group Managers in Organic Group
OK, so intuition told me that this was a can do... Really, membership and controlling the permissions of members is largely what OG is about. 

Anyway, the brief solution that I was looking for is this:


Edit the node containing the group in question from group manager account
Click Group Tab
Click Add people
Add user name
Go back to /admin/people (this is where the magic happens) 
Check the box beside the username in update options.
open dropdown box
Select Administrator member click Update


Voilà! 

There is much more that can be done (for example adding custom roles). Explore on!