Inversion tables are good as a preventive maintenance tool but you must not go back further than 5-15 degrees pass level. This is especially important if you're prone to heart trouble as many suffer heart attacks from this device.
My machine was fine to use within the guidelines above which helped relaxed me but when I tried to relieve my relapsed back injury from work, it made the pain worse.
Just my two cents from experience and research. If you still want one, I have mine packaged in the original box for sale. Paid $170 total, yours for $120 shipped.
Thanks