JC,
I drilled the orifice out on mine. You may or may not have to do this so try it first without drilling. I don't bypass any of the restrictors, valves or solenoids on the engines. I still have the on-board tank in the plane in case I want to use Powermax and use the normal fill port. The fiitings are just stuff I had laying around. The piece on the end is from the plumbing dept I think for an ice maker ($.85 ??). Just solder or JB Weld the correct size of brass tubing for the gas line or festo.

When starting I first open the valve to add some pressure to the system and then close it. I don't use a gauge. After ignition I crack open the valve and listen to the sound of combustion as the engine spools. I can tell by the sound whether or not I have enough or too much gas. You could use the ECU to determine how fast the temp is rising but I usually just listen. I've never had any flames doing it this way and the starts are smooth. I never tried to fill the on board tank with propane, only PowerMax or equivalent gas mix.