I have an old classical with a fairly thin neck that is bowed. I also have a newer Martin Backpacker with a non trussrod neck that has a slight bow as well. I'm planning to set them with fingerboard facing down supported by the nut and the place where the neck joins the body, then strap some weights to the middle of the neck, enough to create a significant back bow, and leave them for several weeks. Any other advice that won't cost me much money? Neither guitar is worth major surgery (like shaving down the fretboard and refretting, having a luthier remove the fretboard to install a truss-rod, etc.).