does anyone know if they run big, small, or average sized compared to most t shirts? im 6' and 175 lbs. ive always been boarderline with medium and large sized shirts, and obviously i cant just try it on. not looking for a super tight fit, nor a super loose fit. if it matters, im 18, so maybe that helps with the idea of the kind of fit a kid my age likes. need some input before i place my order. thanks.