Original post had OPD (I suspect Over Pressure Device), at 15 Pounds. Lol .
Has anyone checked, lately, the pressure temperature chart for propane?
https://images.app.goo.gl/D1J867nPefZQPXZ88
Being a licensed gas technician in natural gas and propane fuels..... there should be a little screw on the side of tank valves, this port is connected to a dip tube that is at 80% full. (Been a while... but there used to be)
Tanks can be filled until liquid comes out that loosened screw.
If anyone questions you, ask to see their qualifications that allow them to fill your tanks.
Just my opinion and qualified to handle propane in my area.
Qualifications vary greatly.
These days I'd have to go to trailer to verify. Lol