Welcome to the new and improved Proflex / K2 Tech Forum!
Well, I've always considered 8" rotors to be overkill on the back of ANY bike, but then, I am not a heavy rider ...(snip)... The only downside to the 8" rotor that I can think of is the extra weight, but I doubt you're overly concerned about that minor difference, considering your bike's build! (snip)