If you do not have a tester, as there are no gauge for regulated pressure on the vulcan 3 you are playing a guessing game.
I run the factory regulator, and had the understanding that Huma regulators would have a gauge on their regulators to somehow ballpark it CUZ i dont think you will be able to 100 % rely on that piece of tape anyway.
So. I have absolutely no idea what kind of pressure i am shooting with in my Vulcan 3, but it is working just fine.
Those extra spacers i have no idea what they are for, in mine you just use the big one.