A couple of things I wonder about....

Mark, These things make me go hmmmmm too.

1. My tach didn't work the last time I tried it.. and I was running my Speed contest engine. I had a std. glowhead/single gasket on a Tee Dee SPI cyl./piston, highflow backplate on suction, 5 x 4 Cox black round-tip prop running Sig Champion 25 fuel. This engine screams.. It was hard to start initially, but increasing to a lg. size fuel line seemed to solve that issue. Now that I could needle and hold a peak rpm, the engine was running with more power and speed than any of my other .049 reedies.. by FAR. I can only imagine the rpm's gained with the 5 x 2 Cox prop I have. I've always run Sig Champion 25 and 35 on my standard cylinders; single and dual bypass with standard glowhead/single gasket. I can't remember the last time I had a plug failure. I've never used a high-comp. head.. or more than one gasket.. (I've never owned a Tee Dee to mess around with tuning) I think that there's several great combinations/configurations for top performance, with a great deal depending on using care in engine assembly.

2. My take on flaps is; they work well with an optimal tail moment combined with the correct stab./elev. areas and SPAN. The flaps are also closer to the prop-blast.. and I would imagine that changing prop/engine could have a dramatic effect on a flapped design. The Ringmaster by comparison, relies solely on it's elevator for turning.. and has that 50/50 split symmetrical tailplane. I would actually like to try designing a stabilator for a conventional profile stunter. A 2 pc. (R/L) connected by telescoping Brass tube running through a Brass bushing in the fuse and secured with a hitch-pin . This "flying stab" design can be easily replaced when damaged or worn.. plus you eliminate having to install hinges!!

The advantage is in the combustion chamber shape more than the compression ratio.

Flaps change the effective incidence of the wing. With the flaps in neutral imagine a line from the leading edge to the trailing edge. In line with and parallel to to the stabilizer and engine thrust line correct? That is the incidence of the wing, in this case it is zero or neutral. The plane will fly along that line. Now give full up and draw the same line from the leading edge to the trailing edge of the flap. That line points up correct? The plane will want to fly along that line. When you move the flaps it'd like rotating the entire wing in the fuselage.

Jim