I think it is easier to mount the controller/fan before connecting any of the motor cables.
I found it difficult to mount the controller with all of the cables plugged in first. I eventually unplugged everything (other than the fan) and it was much easier to place/hold the nuts without the cables pulling and tugging things around. And… all of the cables were actually easier to plug in after the controller was mounted.
and…omg…this kit is incredibly well made and designed. There were several places where something not fitting showed me I was putting it in the wrong place. The photos are fantastic.
