All about the size of the board fitting the waves its designed for, if your short you ride longer and tall vica versa. For example, my son nearly 6'7 tall rides 6'4-6'5 in pretty much everything to 10 feet swell. Shapers keep this in mind and he has been getting customs since about 8 years old. I am about 6'4, don't really have a shortboard currently but my last one about 8 years back and in trunks was 6'5 21.25 x 2.88, at 54 YO now, I would go up an inch and volume next time