My experience is somewhat different. While I have certainly had a few engines that needed specific plug types, I have generally found that most sport engines running on 10% nitro are not at all fussy as to the type of plug. Most of my engines can't tell the difference between an OS #3, #8, Tower generic plug, or even a Fox idle-bar plug.

That changes somewhat as the nitro content rises -- some plugs don't last as long with more nitro & some engines begin to show a specific preference -- but it ain't earth shattering. Similarly, with sport applications, I havent found much difference in engine output between 5% nitro & 15%. At 25% there was definately a difference -- plugs burned out quickly & the engines ran like crap.

My advice is run 5% - 10% nitro & don't get too excited about the plugs.