I just finished installing a Great Plains electronic secondary ignition. I was checking the RPM drop on each system when I realized that my Westach tach is triggered off of the mag so I have no tach on just the secondary. Great for letting me know if the mag just failed, but it presents a problem if I want to run on just the secondary. As far as not seeing the RPM drop to know if a plug is fouled, I am not worried. I know by experience that it is very obvious on the VW when you are running on three cylinders.
I have heard from some people in the past that they only run on the electronic ignition when they are cruising and use the mag for starting, takeoff, and landing. I also know one person with a battery, but no alternator that uses the mag all the time, but the electronic only for takeoff and landing so it doesn't drain the battery. That makes sense, but when you have an alternator is there any good reason not to run them both all the time?
