I also had a lot of fun KAPing before drones. Stabilization was handled fairly easy with a Picavet (or Pendulum) suspension system. Neat and low tech.
More details here: https://en.m.wikipedia.org/wiki/Kite_aerial_photography#Pica...
More details here: https://en.m.wikipedia.org/wiki/Kite_aerial_photography#Pica...
I have been wanting to try it again using a swivel in the line to allow the balloon to spin freely, but then use a tail/fin type of attachment to keep the rig oriented. It seems like anything would have to make it better.