I am working on adding a 30A RV outlet on a pole building but I am having a hard time figuring out the best way to elbow out of the box into the building. I bought a Connecticut Electric 30A outlet box with the knockout on the bottom. What is the proper way to elbow out of the box into a pole building? Most of the 90's I've found convert into conduit, which I'm not sure if I'd need since the siding is so thin. Any suggestions would be greatly appreciated!