Gemini does NOT have upstop wheels. It does have upstops, but they are steel arms positioned below the rail, faced with a bit of brake lining material. In fact, that's one thing that might make for a slightly smoother ride...if the park would update the upstops in the same way that they did on Magnum. The clearance between the upstop and the track is about the same in either case, but on Gemini you can feel a certain amount of violence when the upstop hits the track, making a kind of a banging, scraping sound. A little like the track-seek sound made by certain old Apple "Disk ][" floppy drives. :)
Anyway, Cedar Creek Mine Ride, Gemini, and Magnum XL-200 are mechanically all very similar and probably share a lot of parts. They are all Arrow Runaway Train coasters. Of all the Runaway Train coasters ever built, I'm pretty sure that Magnum XL-200 was the first anywhere to use wheels for the up-stops. And anybody who has ever seen and heard the original Magnum between-rails POV video knows that on that tape you can hear the upstops...which weren't wheels when the ride opened...banging away against the undersides of the hill peaks.
--Dave Althoff, Jr.