SSCX Only!

It's a pomp, got pretty long track ends, more than 2/3 inch anyway. So I think so.

If you're not using a tensioner. You'll have to have the wheel slammed forward for the 20t for this to work. My guess is you need 2/3 inch of rear wheel movement to get this to work well. So it is doable.

42:20 sounds like a nice offroad CX gear.