Light distance from plant

I want to grow a 3 ft plant for personal use in a 38" x 10" x 10" grow box with a 150w HPS and exhaust fan. I've heard that using an HPS exclusively will cause your plants to stretch and grow higher than you want, especially in a 3 ft high space. I've also read that an HPS must be kept at least a foot from the top of the plant at all times, which would reduce the max size my plant could be to only 2 ft . Will I be able to keep the light stationary in the hood at 38" and grow the plant to 3 ft w/o burning it, or will I have to move the plant or light out of the box?