I unsrewed the switch just enough so it was flush with the end of the tailcap. No shim or washer needed, feels just like stock and tailstands now. Can't beat the price.
You can also use an O ring or soft rubber of the right size and thickness to increase the distance from the metal tailcap to retain water resistance being we're using Lithium batteries.
I just looked through my random collection of O rings and washers and found a plumbing (?) O ring approx 3/4" to over-fit the hole and voila..... upstanding fit. A closed cell foam washer (DR.Scholls cornpads) trimmed to fit , should work too? Original O ring idea was posted a year ago in Dmini threads by another CPFr, just giving back.