I am not committed to 4th until the 1/4 mile finish line... going to say a mid gear like the 3.48 or whatever we end up with, I will then utilize 4th gear for mph. I will be quicker out of the hole and more mph available at the end, meaning a faster 1/4 mile... Been there done that in Camaro's many yrs ago... Only problem I foresee with the XF is holding the rear end down, as my last Camaro, had ladder bars, for no torque over, and it would pull the front wheel... We shall see next spring...