I threw my back out again last week, and the drugs have my sleeping pattern all out of whack.  Last night, I spent
another 6 hours researching what other people have done.  One guy reported that he started loosing performance with 2*
of split at speed.  It was a boosted engine on a dyno.  The problem I have with the RX-7 forum is that they are all guys
looking for ridiculous performance running street engines on a dyno.  You have to read between the lines on all of it.
He didn't go any further than 2*, because of the performance drop off, but that fits perfectly with what you're saying
about detonation.

I'm going to go with what I've got now, but I'm seriously reconsidering recasting the mount for the trailing VR sensor
to take out split as a near future project.  There is more to fear from detonation that a little more low end emissions.

> 
> That problem firing a double ended coil is the gap size on the plugs. Use
> plugs you can change the gap on, and set the gap at .010" to .015".
> 
> I used those even with an MSD and never had the problem. Remember the
> rotor is hauling the mixture past the plugs like a freight train.
> AR2592 Autolite work fine. Same heat range as NGK -10s. But usually
> $7.00 a box of 4 at Autozone. The open tip may get better cooling than
> the NGKs

Ok, Lynn.  That deserves some type of reward for being a brain dead simple solution to the root cause of the problem.
If you're not getting a spark because you've set up to much resistance to the current flow, cut back on the resistance.

I learned a bit more about this in the research last night.  You have a couple of very authoritative guys giving very
scientific and clear explanations of why using a split coil won't work.  You have another set of guys going, "Really?
I've been driving that setup for the past 6 months."   The differentiation seems to once again be boost.  So I'm
confident that I can run the single coil set using the wasted spark on the trailing, and I can just swap out the plugs
if it looks like I start missing when the engine is under load.

The ultimate goal, though, is to have two totally independent ignition sources.  The MegaSquirt guys have worked out the
circuitry to run the stock coils or even COP.  The problem I have with that is that it puts ignition control back in the
little homemade box.  I like the idea of having the two highly resilient, time-proven ignition systems that will keep
right on clicking if my fancy little computer goes tits up.  I'll loose control of the advance, but I can be confident
that the limp-home mode of 25* will drag me to crash site.

And that leads me to my next question.  Operationally, what would be the pros/cons of turning off the trailing during
cruise flight?  Will it allow deposit to build up and ensure the plugs are fouled if I ever do REALLY need them?  Or is
it just putting a needless load on my generator in order to dump an incremental amount of extra heat under the cowl?

4 days ago the wife and I were waiting for a light to change at a 6 lane highway in our pristine Dodge Minivan. A moron in a 6,000 pound Trooper II hit is from behind at cruising speed. A witness said he had his head down and was busy TEXTING............... .He fired us into rush hour traffic to the curb lane on the other side, to the stunned surprise of dozens of speeding drivers. Both seats  failed. Seatbacks laid down flat. Both went to the hospital. He has minimum legal insurance. I hired a lawyer. grand Nephew of Woody Hayes. I am going to try for the salvage. I can fix anything. That light had been green for them for a long time and they were up to speed. Why we were not "T" boned with 6 chances, escapes me. 

I used to build totals, and this will just be another one. So My wife can get a newer van and I can drive this one in a few months. Still dizzy myself. No sleep yet. When I close my eyes it plays over again.