Hi again,
I think when you read the sizes they "usually" reach in captivity, it must be remembered that those average figures don`t differentiate between the average for females and the average for males, merely give the overall figures.
I know there are very reliable reports of males getting over 9 feet (2.7m), I think 7 to 8ft males wouldn`t be too rare. The females somewhat smaller (this is V. s. macromaculatus). Of course, the other subspecies reach different adult lengths (on average). "Average" is a great word!!