I hear you there, earlwb. That's a really nice unit there and easy to assemble as it is component lead style wiring to PCB. I was referring to the physical ignition coils, there is a practical limitation on the windings. However, so far people have found a way to hide those units inside the plane.

So, may be some day someone will come up with a miniature flux capacitor to break the 88 miles per hour size limit and provide the jigawatts voltage needed (in my kidding mood).