Dan, since then I got around to working on the big Dyno. I was starting to turn a new contra when I realized that I had not tried to grow the contra piston. In short, I heated it up to a nice glow, let it cool, cleaned it and presto; it fits tighter. I had it mounted on a stand and running in no time. (short runs, cooling in between) It runs well, my tach said 10,400 on a 11x6 wood, (but I think the tach lied.)

So, all's well that ends well! I am happy to have both my AH Dynos running!