Nice, best of luck with Tial. I would say big washer first, then the smaller ones. Doesn't really matter. What does matter is that it doeant leak, the washers won't help with that. You need a thread sealant, something that wont diminish when the gate gets super hot. Gasoila is good, I used it for my fuel/oil lines but it doesn't lock like the blue or red sealant (I forget the name of those, threadlock?). So, I would use a good sealant. Teflon may work, but you're gonna have to load it up because of the taper on the gate threads. Thats why I suggested a liquid, it'll make a nice seal. Just make one straight bead around a thread or two, or use a liquid teflon and go over a lot of threads. Let me know what you come up with