Unirac was very helpful with information, but a few years later they were kind enough to send (they will not sell to end users) me 8 panel clamps to fit 2 more panels on a 15 year old Unirac system. No one stocked them locally and online wanted a minimum order of something like $500.
Used to be called CED Greentech, now they are Greentech Renewables. Like member Ampster, I just walked in and got answers, then years later, spoke with them about those panel clamps already mentioned. They gave me the part number identification I needed after I sent them photos of the old clamps. Invaluable info that allowed me to get what was needed.