Tim, Interesting! Love the photos that you posted. And now I can see from this product ...

https://www.kreitler.com/challenger

... that the rear roller connects to the front. That makes perfect sense now that I see it like that.

Is there a safety aspect to this sort of racing? Do riders ever come off the rollers whilst pedaling all out?

And ... I notice different drum sizes:

https://mrpbike.com/collections/krei...14374491783210

Why would one choose, say, a 2.25" drum over a 4.5"?