Option to disable Post Rank image for admins

[Soldf]

We've been on IPB since the 1.0 in 2002.
For many years our Admins and Moderators have had only the Group Image instead of the Post rank.
As we are a military forum, we reserved the higher ranks for admins  *, **, *** and **** Generals. For users we use post ranks with military rank images from recruits to Colonel. 

Recently we upgraded from 3.4.8 to 4.1 and Admins and Moderators now have both Post Rank and Group Image. I believe it was a setting in previous versions, not some custom code.
But it was so long ago and I don't have access to my old 3.4.8 settings to confirm it.  

Invision Support says there is no such setting in 4.x to disable Post Rank on specific groups. So now Admins and Moderators have two military ranks in their profile, which looks weird. 

We'd like a group setting to set " Enable Post Rank Image: Y/N"

Or does anyone now a work around?

Thanks,

Henke