some info about it
Its called the SG4004 Schleppgeräte and had little performance loss for the mother plane, hard points for under the wing could better be used for other hardware like bombs. The bigger brother of the SG4004a, the SG5041 could hold 5000 kg of fuel, wich could expand the range considerable.
Mothership was a He177A-3, WNr.2236 coded TM+IU