For a shorty there is a kit that has a shaft and stainless mounts and hardware to add a extra set of idlers. On a switch it's more complicated but there again is kit that adds. Idler wheels shaft ,wheels ,stainless mounts and hardware etc. on a switch you move the stocks wheels into different holes , and then additional shaft and wheel set I think you also add or relocated a Cross shaft .this design keeps the rails well supported also doesn't cause a failure point. Both kits are super nice , well designed,work