When my grand daughter & I run short on the batting we call it Frankensteining the batting when adding more batting to the existing batting lol she doesn't like doing it but I sure will to save future problems lol. I love quilting with her, actually I should say sewing with her. She will make a quilt but doesn't want to quilt it just do the birthing method & call it done lol.

Yes, this is what I do. But since it is on your frame, if the cut is straight, with some spray adhesive, I would butt up another piece as close as possible. I think it happens to everyone at least once if not more!!