I am alittle confused here. You tell the man that running colder plugs is not good but YOU run a step colder plug. I understand the other stuff but then you say a step colder heat range is better. Maybe not 2 or 3 steps higher then???:Shrug:
Normally 2 steps colder in a stock engine isn't a good thing, it may be too cold. But since HD has been running them lean a person can get away with it. I like to run 1 step colder in high compression engines which my 120 is 10.5:1. When it came to running them in my dads Triglide I trialled them in the 2010 Triglide I used to own 1st, then put them in my dads and made sure they were working as they should. I didn't go to one step colder in the Trikes for any operational issues or reasons, just didn't feel like keeping 2 different heat ranges of plugs laying around.
The risk a person does run is a colder plug may have a fouling issue, all you need is a valve seal to start passing or start moving a little oil past the rings and you could be fouling plugs.