The product is good, decently built, and great price Only to simple advisable changes.
First, The rails get bent with the nut pressure, so a reenforced steel bracket to the side of the nut will prevent this and the entire rail does not need to be reenforced. This will help keep the price low.
Second, please make an instruction video or manual. The only available videos are Youtube videos from individuals.
All in all the but is good and worth it.