That decision is made early-on on I-day, when the males are getting their hair cut for the first time. It's not too stressful by itself, the only people who I know got their hair cut either asked for it, or it physically could not be put into regs, (3 inch bulk all around). The female cadre working the hair station know you're stressed and nervous so it was a pretty relaxed environment, that being said don't plan on taking any more than 30 seconds--you'll appreciate being able to do it quickly in the mornings