made4surf suggested the link:
http://forum.ih8mud.com/60-series-wagons/174829-two-up-single-kaymar-tire-carrier.html.
This was my solution for a recent 4000 mile / 3 week trip in Baja. I was initially concerned about the weight and cantilever on the Kaymar tire carrier, but it performed well.
There was a bit of bouncing that occured on the California highway sections where expansion joints (at regular 20ft. centers) would set up a harmonic. If it got too excessive, a lane change would generally take care of the cadence problem. Otherwise...asphalt, graded dirt or trail work...no issues.
IMO a compact and cost effective way of carrying an additional spare.