During testing at Obertraubling initially three He 111s were used to tow the Me 321,later reduced to two. The difficulty of maintaining position was also a factor in the decision to try to use one tow aircraft like the He 111 "zwilling".
The Me 321 could however be towed by a single Ju 90.
The first Ju 90 tow ended in disaster when the tow snapped at around 500m and the glider dived into a forest near Kelheim killing all on board.
Three Bf 110s could do the job but it was as dangerous as it looks.
On 24th June 1941 there was the first fatal accident with the "troika" system when one of the towing Bf 110s suddenly and inexplicably veered of towards the Fliegerhorst motor transport sheds and crashed,killing the crew.Towing accidents continued on acceptance flights,the Bf 110s suffering more than their fair share.
This is the wreckage of a Bf 110 tow aircraft in which Unteroffizier Erhardt (pilot) and Gefreiter Greiner (radio) died.
All this was just on test and acceptance flights,generally with unladen gliders and always with highly experienced pilots flying the tow planes.
It's for a different thread,but having read many of the first hand accounts of the glider pilots the Me 321 might qualify as a clunker.
Cheers
Steve