Im at 15/41 myself. It will give you a noticable improvement in low end. I have a 43 tooth sprocket that i will probably put on this weekend. If you go down one tooth on the front you can use your stock chain. It will throw your speedo off by roughly 6%. I got a speedohealer for my bike simple to install opening the packing box took longer than the install lol. Corrected my speedo and also gave me a top speed recall button. Your bike will be a little more wheelie happy in the low gears so that is also something to think about. You wont lose any top speed by going down one tooth. The superhawk with stock gearing runs out of steam before it runs out of gear. The lower gear ratio will only get you closer to a good balance

 

I'm -1 up front and my speedo is off by about 14%, I am using stock chain, shouldn't notice much shifting difference, but you will have trouble keeping the front down. I have read that the lack of a slipper clutch was what kept the sHawk's 1/4 mile times higher than optimal... also have read that it was the 1/4 mile king in it's day.