I highly doubt you were riding when Scramblers were at their height, let alone when light weight race bikes became available to purchase from the dealers. Scramblers and desert sleds went away simply due to the advancement of lightweight two strokes. Now lightweight high performance four strokes dominate. The key here is weight and ability to un-weight the front end of the bike and that is where the 21" shines. The OP here on this thread is taking about a bike (550 lb 1200cc Sportster) that weighs TWICE what a high performance bike does. A bike with a heavy front end that has a tendency to plow will benefit from a 19" wheel with a wide tire. IF you were racing back in the day of desert sleds and the big front end heavy Greeves show in my pics, you would know that indeed 19" wheels were far superior. There was a reason they were used, simply because they worked. I know, I speaking from personal experience, I was racing the dez in the 60's and I still race the dez today. Duh..... no one is racing bikes that benefit from running the 19" wheel any more, but that doesn't mean that when they did race them, they didn't benefit from them. And as you say, NO ONE (not even Mouse or JRC) are racing a 550lb Sporter either.