with most "new" orings you will find the cap does not crush on the orings much if at all. the silicone mugen uses does swell, and so this shimming technique is just making more room for this. yes you could just sand down the white bushings to achieve the same objective, the shims we advised is just the lazy way out.
I have not encountered any leaking yet after a year of doing this and I strive that my seal stack has no preload via the cap. I remember when I was testing swell resistant orings (like kyosho ones) but having even worse stiction than the stock mugen which are actually very slippery AFTER they swell! my guess is the mugen material absorbs silicone oil subsequently providing lubrication. whereas my swell free orings did not and I assume clean rubber on chrome is not a great bearing or that just did not react well with silicone oil.
I do remember the green slime from the RCPS days. (oh geez I am an RC troglodyte!) I am sure it will work very well, the mugen orings do seem to react with silicone oil very well (although not in a way we would think) while some other oring materials don't, cause silicone is generally a lousy lubricant to begin with. green slime is a good solution if the orings you have don't play nice with silicone oil. I was having to grease my "alternate" orings to get them to work better. although I was using "slick honey".
and yes this is truly anal 10/10ths stuff. although it was Cliff Lett at the '91 worlds in detroit that taught me shocks were everything after I saw him redoing his after almost every run.
