You can order the FPE 2.4 with Ridge or CH Synco-spark(Brison is CH mechanical advance). The CH Syncro-spark ignition give you about 400-500 RPM increase over the Ridge. Both are a good combo for the Sig Extra. A person at our field has a Sig Extra with the FPE 2.4 and Ridge ignition, its vertical is unlimited. I have one in a Hanger 9 Edge and love it. The thing that is most impressive is FPE's customer service.The CH version is not needed for this plane but they seem to sell better used if you ever wanted to.