As long as you are familiar with the landmarks on the snakes body and use the proper technique popping and probing are safe. You will need to be visually instructed by someone experienced in the procedures. However practice will be your biggest confidence builder. Also the number of sub caudal scales is another determinating factor in sex identification. Snakes grow throughout their lives, they don't ever stop growing. As evidenced by the lifelong shedding that they do. It's called indeterminate growth.