Pantherman,
Here's a few quick words on Festo fittings.
There are two side of our fuel systems 1: Suction 2: Pressure. The pump draws (sucks) fuel from the tanks, and then pumps it to the engine under aboout 80-90 lbs pressure at full cooker.
Festo and other instant tube fittings are designed to operate under pressure. Not suction. They will work on suction, but you need to follow some easy rules:
1. Avoid sharp small radius bends at either end of the fitting. Make sure that the bend is very gradual, or air can leak between the conical sealing element inside the fitting and the ID of the tubing, and allow a nice stream of air bubbles into the fuel line.

2. Make sure that the mating end of the line is cut very square with a sharp razor or plastic tubing cutoff tool.
You don't need any air bubbles upstream of the pump. If the pump doesn't process the bubbles, a flame-out is in store for ya. Could be very ugly.

On the pressure side of the system, avoiding tight bends is smart, but the air leak isn't much of a problem. I install either a Festo 4MM ball valve or a JetCat ball valve in the pressure line to the engine, and another one in the pressure line to the kero-start heater element.
Safety wire all of the barbed fittings with .020 safety wire to prevent leaks.

I prefer to avoid Festo fittings on the suction side entirely except for the UAT filler line, on which I use a Festo 6MM plug in check valve. (P/N QSK-6)

Good luck to you....

Harley Condra
BVM REP
JetCat REP