Do they make 6 feet flex pipe ?  I was planning on using the 3/4 ” black iron. I will have to look at the rigid pipe…  They sell that at Lowes ? lol

Keep in mind that flex pipe is easily 10x more expensive than using black iron.  I have about 14 feet of black iron going from the outside of my trailer, up through the Ansul system, and then a couple of 90degrees – then I use a shut off at the terminal of the iron pipe and run a flex pipe from the shut off up to the appliance.

Oh, and I also use flex pipe going from the LPG regulator to the black pipe inlet.

I think off the top of my head, a 3/4″ flex pipe (the yellow coated ones) about 2′ long was about $40.

About one of your other questions – I use a 2 stage LPG regulator commonly found in RV’s.  I draw about 150,000btu and it’s good for up to 160,000 – cost about $25.