Summary

The original STL has right and left rails in one file. I just cut off the left one with Meshmixer. If you need the left rail, just mirror the right rail.

It took around 10+ hours to print with CR-10 and 0.6mm nozzle. Therefore, I like to print one at a time. The rails were printed with PLA+ 20% infill and extended arms were printed by PETG with 50% infill.