Oh boy, you have asked a huge question when you look at the variables of bike, your size, your preference etc. I'll give you a thought based on sense and logic more than preference. I too have a Challenger. I"m 5" 11". So, I took got the 11" (8.5" from the cutout to the top tip). I too thought it was too short. So I bought the Indian 16" (14.5" from cutout to top tip). The 16" works fine but then you have to look through the windshield which I prefer not to do. So I changed them again and the 11" factory didn't have too much buffeting so I've kept it. I actually run it down about 1" so i can see well over it. You will have to buy an aftermarket windshield to get your 12" or 13". Then, if you were my size, you would have to put it down so the tip is not in your sight line and you will have gained nothing. If you are shorter, you will have to look through a windshield. If 2-3 inches taller, you will be fine. But using sense and logic, you have little to gain and some good money to lose if you are wrong. One suggestion for you is this. Tape another 2-3" of sturdy cardboard on top of what you have and test it out. It might tell you enough for you to make a decision. Only you can tell if you want to look over or through a windshield. I've done both and for many years. My preference is over but through is very doable for me. Hope this helps you.