My guess is you are using a low stretch string like poly. Start with you weight down and left it slowly in small increments and let it down slowly.
But then how do you clamp a single string with flying clamps. if you had a starting clamp you could clamp the right main outside the frame with the SC and tension the left main then you have two strings to clamp.
I have the ability to drive people crazy, not sure if I was born with it or I learned it but I'm damn good at it.