This may come as a complete shock to many folks but dual plugs ain't what most think. We have dual-plugged Pans, Iron & Evo XL's, Shovels, Evo's and Twin Cams, over the almost 3 decades we have been in business.
Small engines, as well as large powerplants.
NEVER had we EVER experienced anything earth-shattering, in regards to doing so, while dyno testing/tuning later, and trust me, we shook the trees.
Machine heads, 4 plugs, 2 sets of wires, multiple coils, specialty coil mounts, usually along with a single fire ignition.
Let's see...........650.00 plus dollars for no more torque, or hp, in a street driven bike.
Think I'd rather have a bar of soap.