30 miles towing was with the outboard at under 6 knots (maybe closer to 5.5 or 5.4 knots). When I did sail the sailboat on that trip, the 17 YO son would sail along in the AI. Don will probably know where these points are but on that trip, we went all the way from the near the "sandbar" at the North end of the lake to Parker dam and stayed one night at Steamboat cove. At Lake Powell, I pulled the AI and the two kayaks floating off the back around 90 to 100 miles but as mentioned, I think the drag of the kayaks hooked to the back of the AI helped the stability.
I also had the tow rope going through a some sort of attachement at the bow and then clipped to the mast. However, when I look at the picture I posted above in this thread, it looks like the rope had wrapped around the hull one time and I didnt notice it probably since it was still pulling from the spot on the bow.
FYI, the towing hasnt seemed to hurt anything, my AI after 3 (or maybe its 4?) years of lots of torture is still in fairly good shape
picture below is from Lake Powell - towed like this 90 to 100 miles