As I mentioned on another forum, the C5 Z 6th gear is .57 while the regular C5 six speed 6th is .50. Through the years, the various forum members have reported a C5 Z06 top speed as between 171-174 MPH. Too high for me, but I got 20 years of thrills flying my Mach 2 F-4 Phantom!!!! and, my takeoffs only exceed my landings by one!!!!