I finally installed one of the two SD spring kits I ordered (I was the OP for this thread!). I now have one SD that is fully modified and the other that has only the Apex striker spring (lazy - I know - the trigger return spring will go in soon).

I'll be at the range tomorrow night, shooting a variety of 40 S&W rounds, including Speer factory and handloaded with CCI and Federal primers. My only concern is primer strikes with the lighter striker spring -- proof of concept tomorrow night!