That will depend on size and attitude. Size is important because if you weigh 90 lbs and the snake weighs 20, you're going to lose in a tug-o-war. If you're not tiny, then your attitude will be important. You have to know your snake and be confident in your ability to handle it.
The large snake guidelines are good but with boas it can be difficult to know when you need a second person. They are, as a rule, much more mellow than pythons. In my experience.
The thing is, while you really should have someone there when the snake is 8 ft or larger, you may not ever need them.
I say train your husband better and be done with it.