NO, you Lunatic!! you don't mix compounds!
least it's no advisable for the track (maybe street is okay if you're not driving like a Lunatic... but I get the feeling that's not you!) LOL jk
but regardless, your rears will wear out much quicker than the fronts as the 'R's' are a much softer compound... better for traction sure, but for lessor period of time, we don't need you whining about tires every two months Sir!