The reason you don't see much in the archives since 2009 has to do with the complete redesign of the frame, swingarm, and engine mounting system that occurred for the 2009 model year. While still not perfect, the result is so much better than what existed previously that MOST owners of the late model bikes have seen no need to install devices that were designed for the old "flexible flyer" design that ran from around 1980 up through 2008. Even though the need has been eliminated or greatly reduced, the folks selling the various stabilizer products have continued to promote their products as if we were still back in the old days. Placebo or actual measureable benefit is up to each individual I suppose, but IF the stock setup isn't worn or out of spec for whatever reason, I'd guess more placebo. And if there really is something wrong with the bike, I think I'd rather spend the money to fix the real problem versus spending $500 on a bandaid that may partially cover up the real problem. But that's just me and how I view things.
As for the strange feeling in the twisties, once the tire starts to become squared off you can expect that regardless of the rigidity of the swingarm and mounts. It's been that way on every bike I've ever owned, not just Harley's, and you don't necessarily realize how the feel has changed until you mount a new tire. How did the bike feel when the tire was new?
There is no valid alternative to the Harley branded Dunlop 18" rear btw. You have to look at load rating and the rim width the tire was designed for, and the stock rims are only 5.00" wide. So even if someone did have an 18" tire with the proper load range, most 180-18" tires I've researched require a wider rim. Harley got you guys good. Anyone who absolutely wants to go with different tires needs to change the stock wheels to something else that is compatible with tires that are available elsewhere. That would be an expensive proposition, and explains why very few have decided to go that route.
Jerry