My opinion... You are there. Unless your string is 1/4 inch rope.

I'd guess you have already begun to lay down the strips, if not then I would start...

Course, then I'm not the artisan that some are... though I am trying to move that direction...

Still,if you are arguing with yourself about measurements that fine, you may be an artisan yourself.

For what it matters, sounds like you could back the screw out half a turn, put a toothpick or sliver between the form and the frame, turn the screw back in, and get it perfect. Of course, as soon as you staple to it or use the form as a base to clamp to, you will move it a little... so just begin.

Rick