I asked Chris Neff that same question on FB:
Dear Chris,
Can you help me? You say that there is a "line" on tops where the string should be wound to. Where is this "line " on the Giulia, and how long should my Giulia string be?
Thank you,
Tyler Young
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Reply:
"Hey there Tyler! if you are using the thickness of string that it came with, it should be pretty long, like 70 inches. If you get some fatter string like Spintastics "large" string, it could be shorter, like 64 inches. If you stuck a ruler into the gap of the tip and measure up the line is a little under 1 and a half inches."
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Good luck.