I acquired a Mac's 8.5 muffled pipe and extra long header for my O.S. .55 AX, the chosen power plant for the Vertigo II. I dialed in the pipe on the ground, and was able to achieve 14,040 RPM with an 11-7 APC prop, burning 12% Cool Power/Omega mix fuel. I am impressed with the output of this engine, and I am happy with the effectiveness of the pipe which netted a gain of about 1500 RPM. I set off to the airfield with it mounted in my test airplane (Graupner Skylark/57" span/6lb empty). With this fairly light airplane, it had vertical performance more akin to a Quickee 500 than a pattern plane. Quite the ballistic performance. I am confident that if I am diligent with weight control on the Vertigo, It will yield reasonably good performance, at least for the prototype.