Honestly, I wouldn't worry too much about people believing you. When people see you producing visuals they will tend to believe you on the hets. I generally take a picture of the whole clutch which shows the visuals and the hets. Some people I sell to want paperwork, and some don't care. I think paperwork is pretty worthless and never ask for it when I am buying hets. One of the first guys to give out paperwork turned out to be a scammer.