Ok.... so I went out and got out the flaring tool and started playing. I see the issues you guys are having. I honestly haven't ever needed to make any of these. I have the tool, I saw the fitting and just thought "yeah, that will work". Should have attempted it, so for that I'm sorry. I think the washer idea is ok as long as it sits flush. I tried it and it cocks in the bore. I don't like the double o-ring deal in your pic though. I don't have any 3/8" line here to play with.... apparently, I'm out. Keep trying guys and I'll get some 3/8" line and see what I can come up with. I still don't like tapping the valve, but it may work. If you are going to try that, I'd suggest going to a o-ring face seal and not pipe.... but I'd have to scour the taps in the tool books and see where to even get that thread tap.
Good going, really! Just keep trying.
