The Wall

You have a party and there is a wall with an opening.  Two subs are
bent over through opening in the wall with only hands and head on one
side and the rest of them on the other.  The subs are facing opposite
directions so there is a 'complete' sub on each side of the wall.
The head part is in charge of the body parts on her side of the wall.
Guests get to do whatever the head on their side allows them to do to
the body part on their side or whatever the head encourages them to do.

The wall is soundproof as is the bondage holding them in the wall so
they can't hear what is happening on the other side, just feel it when
it happens to them.

If you have 4 subs you could have 4 rooms with a common corner.  This way
the head is in charge of the 'body' that is 3 rooms away.