Been picking up some of the S-mods lately. A couple have needed tweaking, and today I got to tackle the #19 ("a", I guess, doesn't look like that "b" pic).
Anywho, looking at the fixes so far and what I had after managing to get the switch apart, I took what I think is a slightly different approach that I do not recall seeing here before. If this has been posted before, please forgive me - it's becoming a long thread.
Using a couple pairs of pliers, I twisted the spring back against itself a bit at a time until the diameter was larger, and could be snuggly squeezed inside the body of the switch base (making contact with the sides all the way up to the Delrin insert). Then just put it all back together - the spring still makes good contact with the switch button when assembled.
This reverse-twisting seems to have the added effect of making the spring slightly shorter and/or just easier to compress.
Inserted in the switch body this way, the path is from battery Ground to center post, center post to switch button, button to spring, spring to switch base, switch base to body. No extra wires or tabs required.
Seems to work pretty well. Got rid of my intermittent firing and sparking/shocking I'd get once in awhile. Haven't bothered measuring for any additional drop, but it's hitting pretty well so not worried about the numbers.
Just thought I'd throw that out there in case it hasn't come up before. Seems a bit easier for someone who may not have a lot of other tools handy.