The washers are to effect the throw length, add a washer for a really short throw, take one or more out for a longer throw. Before the recessed switch update I have usually seen them come with 3 washers installed and one extra in the bag, I like the throw with one or two at the most, but again, that's the old switch.
Bodog take the top cap off, unscrew the pin from the bottom a couple of turns. Now unscrew the pin from the top until it is high enough to screw your atty in and leave a gap for now until you get the process down. Some can be loose and they aren't reverse threaded so if you just keep turning the atty it can screw down the pin so try to avoid that by leaving a gap and just screwing the atty down enough to make make contact. Now the key is flip it back over and screw from the bottom until it is tight, you will feel it firm up and that should keep it tight from the top as well. If you can't get it down maybe I could make a video, if not contact HoH about it. Mike has the best customer service in the biz, he will make it right.
And it doesn't matter what Zen you have, ZNA, DX, 2.0-2.1-2.2 the link will screw in to all of them because they all have standard Z2 threading.
And Xenon I'm not gonna bother arguing much with you since it's clear you have made up your mind but Mike is one of the best manufacturers in the business for a long list of reasons. 1 volt drop where are you getting this? Hearsay? How did you test it? Maybe at .08 ohms which most any PV would be. His stuff isn't made for low sub ohming below like .3, if you want to go there they sell a low ohm kit. His PVs are made for regular users and they work extremely well for that.
The battery rattle is ages ago, I don't know why people keep bringing that up, and it was for a very good reason, to prevent arcing from the battery to the contacts. If you have rattle on a remotely new Zen PV you aren't setting it up right.