With mine, I have to open the valve on the tank slowly otherwise, I get low output. There is a Overflow Protection Device on propane tanks (I think thats what its called). It took like 4 hours to boil 6 gallons. On my regulator, I adjust the flame that I need
I would worry about not being able to inspect the inside of the tube. If is not completely clean and dry inside, you will run the risk of verdigris forming the pipe. Verdigris will make you very sick.
I have Sterling and Crystal doing the best. The Cascade, Centennial, and Kent Golding are not growing as well. the first two get morning sun and shade the rest of the day. The others get much more sun.