I personally wouldn't feel safe using that unit either.
When I had a SCT I attached a rail-type piggy back mount. It attaches at the front and rear of the optical tube assembly. A slide mount allows you to move the camera back and forward on the rail. This is helpful when shooting wide field to be able to slide the camera forward to get the telescope out of frame in the foreground, especially if you're using a dew shield. The rail mount having two points of connection are much sturdier than the single type you ask about. Here's what mine looked like:
With that said I don't know if I'd feel comfortable piggy backing anything too heavy on a one arm Altazimuth mount. It may create some balance/tracking issues and possibly stress the mount but I can't say that for certain since I've never tried. I would think as long as you stay well below the load capacity you should be fine.