George,
Yes, it looks like a bolt head in the valve stem hole. Since this is the first time that I've done this, and my only experience with it, I can't say what it would take to remove the tire and put on a new one. Since my tires are for commercial use and have a ten ply rating, I would have thought that would work. But taking out trees in the woods is just more then they can handle. I never take it out on the pavement, so wear on the tread should be minimal. I don't foresee replacing the tires, but if it happens, I'll foam them again.
As for the ride, all I can say is that I haven't noticed a difference. I keep them at 35psi, so the ride with an empty bucket seems the same. One thing that I haven't done yet, but I'm curious about, is what it will be like with a heavy load in the bucket. At 4,000 pounds of lift on my loader, I can put allot of weight on my front tires. I've seen them flatten out pretty good under a big load, like a stump. I'm hoping that with the foam, it won't affect the shape of the tire.
As for being able to patch a tire with Slime, that may be true, but getting a repair shop to do it for you is another matter. I've been to several shops and have been told the same thing, you can't patch a tire that has had slime in it. The only way to fix a flat after you have put Slime in it is to put a tube into the tire. Of course, when the Tube gets a flat, you can patch the tube if it's repairable. I've been about 50/50 on getting tubes patched. Sometimes I can, other times I have to buy a new tube.
Eddie