Do not sdjust the factory gap beyond a check to see that all plugs have the same gap!  Your (Slick) mags aren't up to a .024" gap if you should loose the pressurized air supplied to the mags.  These are fine magnetos and will serve you well as will the iridium plugs but don't mess with factory settings!
Walter Dodson 1895740 IA.
ps: at .016" gap you need not pull the hard to reach top plugs each 100 hr inspection as long as the rest look good.  Do those plugs every 300 hrs when you clean your injectors in your ultrasonic cleaner.