I would not cut the string in half. I would make a 10' short side and 30' long side. When you finish the mains tie off and use the left over on the long side for your next string job. That will leave you the maximum length for the second time around. If 10.5' for each side worked for poly (half of 21') then 10' should work for gut. Any way it goes you will know next time.
Originally Posted by Lakers4Life
Invest in a staring clamp, it will save you a lot of headaches.
He did say he had a starting clamp I thought.