I have towed signs and banners.

I hooked the towline to a release at the tail.

I found very few drawbacks to flight with the banner on.
Pitch was slow, but the plane turned fine. Rolls and inverted were also OK.

Plus side , all adverse yaw was eliminated by the drag of the banner.
I've towed with Aeromasters and Sportmasters and even a Falcon 56 all without problems.