David,
As mentioned in my post, I have a 13B rotor housing on my work bench. I can get a rotor side view of the plug ends. There is room to move the leading plug tip closer to the apex surface of the housing.Even without the sealing washer there is at least 30-40+thousandths to spare. Unlike most combustion chambers, the plug electrodes do not project into the the chamber and mix, but must ignite the fuel mix from a recess as the rotary engines (difficult to efficiently combust) mix whips by at high rpm. I'm thinking that moving the plug end as close as safely possible,and by using a single ground electrode to provide space for a little eddy of mix to engulf the spark . This might allow better initial and thus better overall combustion. Paul Yaw has kicked this subject around on his web site in the past. I've experimented with a stock plug with 3 of the 4 grounding straps removed and noticed a difference, Mazdaspeed sells thinner washers for there racing plugs with a note that moving the plug closer to the mix showed HP gains. I've talked to an IT RX-7 racer in the south that runs a single electrode plug without the washer and swears that this "wakes up this engine" So I think that this is worth pursuing,especially in light of the fact that rotary engines arn't very efficient and usually due to incomplete combustion.Anything that improves this shows up all around the track.
I figure that there are some rotary guys out ther that have played around with this that might share their findings.
Thanks,
Brian