The motor box comes simply taped together. It's up to you how you go about centering the motor to the cowling, and how to get the distance out to the front of the cowl right. My buddy brought over his new laser level (wide beam for mounting shelves, etc.) and we established a position on the firewall. These new household lasers are fantastic for model building. Anyway, after cutting the motor box back about 1.75", I had the distance close for my YS140sport. Here is a very poor picture of the mounted YS motor....and in the cowl...