I have an old center-pole double chair. I made a swing set-like frame out of 4x4s, with 2 4x4s running across the top, between the A-Frames. In the center of that span, I put a piece of 1" threaded galanized iron pipe (buy it at Home Depot, etc). I drilled half way into each of the 4x4s, so that once the whole thing was assembled, the pipe could not come out. I clamped the chair to the pipe the same way it clamps to a cable. It worked very well and allowed the chair to swing in all directions. I made the support structure big enough that the swing could swing side to side a fair amount, and tall enough that I could keep the swing-in foot rests on it. I think I used 12' 4x4s as the legs, because the chair is about 10' tall. Unfortunately my only pictures are film prints, and I never reassembled the structure when I moved to my current house a few years ago. I was going to hang the chair in my screened porch, but never got around to it. So the chair is currently under my deck waiting for us to move again (very shortly). I've promised my daughter I'd put it up at the new house when we move.