the best way to purge the uat is to hook 1.5 volts to your fuel pump after filling everything, and let it run. Just use a AA battery and a couple of wires. take the output of the pump and dump it into the same can you are drawing the fuel into the UAT from through tygon or 6mm. Let it run and shake the uat, and tap it and eventually all the bubbles will quit. then let it sit and soak for a bit, and repeat. It took me about 30 min to get rid of the bubbles AFTER I had a flameout. I suspect I got a bubble, but not really sure. Take the time to get the air out, its time well invested. Once saturated, it will give years of pleasure.

The Wren pump, both the Hasl and Flight works has a 4mm input and a 3mm output. Its really tight but the 3mm will go on it on the pressure side. You will need to get a reducer to go from 6mm to 4mm. I would strongly suggest a simple brass 6 to 4 barb available from dreamworks.

The output of the pump to the motor should never be tygon. it has to be hardside tubing. it will go. safety wire it when done.

I use 6mm tubing for my feed line, but alot of guys use tygon successfully. If you want your shutoff on the pressure side, you can put a 3mm festo cutoff or barbed cutoff somewhere after the pump.

Generally speaking festo is designed for pressure not suction, but alot of guys use it on suction side with hardside tubing.