Ok, this is a bit odd, but I'm soliciting opinions. Let's say a person had a VW engine with heads machined for dual plugs. Now let's say the person had a single-plug ignition system, and wasn't inclined to upgrade. What's a person to do? The way I see it, there'd be two options; option 1, put spark plugs in all the holes and ignore half of them (or make some dummy plugs to save half an ounce), or option 2, come up with a wiring scheme that allowed a flip of a switch to swap between banks of plugs as a backup (in the event that a plug failed mid-flight.) My concern is that you've got several small bits of metal hanging out in the ignition chamber just waiting to cause preignition; in addition, I'm curious as to whether you'd have excessive carbon build-up on the unused plugs, to the point where they wouldn't fire if called upon to do so. Has anyone played around with this, or something similar?