Larger Size for Feel on Hands
It appears someone may have put in a larger size line in, not for the strength required but for ease of handling - it doesn't cut through the skin so much. While the 3/8-inch would probably be adequate for strength, if the blocks will accept 7/16, you might consider this just for ease on your, or your crews, hands. Under normal use the line will probably last around 10 years to initial cost should not be the only consideration. Just a suggestion.