Piston engine aircraft engines have used multiple ground strap spark plugs for years, they have two plugs per cylinder and two magnetos also.
They would last about 500 hours in my 260 HP Lycoming 540 C.I. opposed flat six cylinder air cool engine.
They call for .016 air gap on both sides and I would have to gap them again after around one hundred hours due to wear on the center ground electrode and a little wear on the plug straps work The instructions called for replacing them after the center electrode started looking a lot like a football instead of a baseball, which they would get like shruggy
Nothing magical or better about them is my impression, not cheap though either shruggy
Seems like several years back there was another attempt by a different company to market multiple ground strap spark plugs which never gain popularity or a large enough use to keep the company in business work shruggy

Last edited by Cab_Burge; 09/23/17 03:03 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)