There is a picture on the net with 9 (yes Nine) gliders on tow!

If some one cannot come up with a link, I will send you a copy direct..

I've actually seen a video with such (that?) aerotow. IIRC it was done
for a music video clip.

Too bad I can neither find anything about the band nor the video. It
could have been in Belgium or Netherlands...

I think it was recorded as a world record, too.