
One thing you could do to help bring those panels in (as long as them are almost parallel), instead of one stitch that bridges the panels, drill another hole in each panel close to where the stitch is, put a wire loop in each panel, then put a wooden dowel captured by each loop so that the dowel bridges the panel, then start tightening the loops.
That was a tip from MulletKey from way back.
You can kinda see what I am saying this this picture from my WF build. It is only the small dowel near the front. The longer dowels just a little ways back from that one are used to pull the panels in to the frames.

DM