Amazing this thread is still going after 6 years! I just came across it. I read in here a lot but never comment. This however prompted me to say something.
Larry, did you ever get your tires mounted? I ask, because I used to collect Eclipse mowers (before Hahn bought out the Eclipse company of Prophetstown, IL) they used the same wheel/tires. Hard rubber semi-pneumatic. I had several old reels, manual and powered. (Google Eclipse Rocket or Parkhound for an example) An uncle of mine told me he used to have to replace those tires when he worked at the hardware store as a kid. Said they'd cut the old one off, clean the rim, then heat the new tire in a pot of oil. It would soften and expand in the heat. You pull it out of the oil and you'd have about 30 seconds to get the tire on before it cools too much to get it on the rim and have to try again. As it cooled, it contracted to the rim, nice and tight. I never tried this myself, as I just displayed them as they were, but perhaps this little tip can help someone else down the road.
"Said they'd cut the old one off" I didn't have to do that, and I showed the old tire and the rim it was removed from in Post #1. As you said, that was six years ago, so I don't remember exactly how I got the old one off an the new one on, but it wasn't very difficult to do. I do recall lubricating the new tire and using big C clamps to persuade it to slip onto the rim. Most of my mowing is done with a ZTR, but I have some hills I won't use it on, so I have to do those with a walk-behind. The Hahn Eclipse was for those, but I replaced it with a 15HP, 36" BOP mower a few years back and therefore haven't been using the Hahn Eclipse. I drained the gas from it and it's been sitting unused ever since. I still think it's a good mower, however.