I don't think the C-47s dropped troops and towed a glider at the same time. The C-47 was rated for a 5000# payload (7000# emergency payload). 28 jumpers at 200# X 28 is a bit over 5000#. From what I've read the gliders were used for vehicles and small field guns that couldn't be dropped back then.
Seems like the stalling speed of a fully-loaded C-47 could be perilously close to the cruising or even maximum speed of a C-47 towing a glider, if such a combination could even get into the air. But I await informed opinion here.
