Installing a vent free 30,000BTU propane wall heater. Supply line through exterior wall underneath.

Hello, I'm installing a wall mounted vent free 30,000BTU propane heater. I need to install the supply line directly through the exterior wall underneath the heater to the outside. The propane company said they usually just hook up to a 3/4" black pipe on the exterior. Can I simply just put a solid piece of Threaded 3/4" black pipe through the wall and use a flexible pipe from there to the wall heater? They bring the line to the outside connection, provide the 2 stage regulator, and do a leak test. I have nothing else I'm using gas for and I want to keep this as simple as possible.