Limiting upward growth?

[Revanche21]

I'm growing in a "grow box" and the height inside of it is fairly limited, about 30 inches. I intended to top the plants to control this but after reading more about topping I don't think that is the answer. I think after topping I will still get upward growth.


Does anyone know how to limit a plant's height affectively without risking harm to the plant?

Thanks.

LST low stress training
bending the plants