Santa gave me 2 Harken #007 dbl 3" blocks for x-mas. They are to be used for my main sheet as a 4:1 purchase instead of the 1:1 that I have now on my H310. Having just made a trip to the boat and endured -10 deg. wind chill temps. to see how to mount the blocks on the, I could not figure out how to replace the block on the traveler. Not wanting to be outside very long when it's that cold, I came home with no ideas. I know that many of you with arches on your boat have switched to the 4:1, How did you mount the block on the traverler car? Will I need to replace the main sheet line to accommodate for the 4:1 purchase? Thanks for your input. Steve, s/v Odssey H310 a.k.a Obsession....