The CORRECT way to fill a DOT tank.
1. Fill is by WEIGHT. Nothing else. Weight is the ONLY safe way to fill
2. The REASON to open the "vent" screw and you do this even by weight fill is to STOP the fill when Liquid LP spews out. That indicates the correct 80 percent level has been reached
3. IF the Idiot filler is filling by waiting for the OPD to shut off, that is dangerous and I would not hesitate to tell him NO. OPD's are not installed for filling only. It is a extra safety when filling if the weight scale is off calibration or they do not fill by weight.
4. Last, if you do not want to correct an incorrect fill of YOUR tank, then it is YOUR safety that is compromised, not the ignorant filler. The unsafe level and potential problems will happen after you leave. Doug