I live at 2700' altitude and the DA gets to the 5-6000' level all the time. I ride up in the Angeles Crest and it goes up to 7000' max. I went 16/42 and I wheelied so bad I could not even get down the strip. But, I am a wimp. Then I went 17/42 and ran my best ET until tonight hitting the rev limiter in 3rd before I got to the end of the 1/4. Next I ordered a 41T rear sprocket and I am running that right now. My SpeedoHealer shows that I hit 134 at the rev limiter with the 41T rear and I go through the 1/4 at a max of just over 132. Using the 134 for the 41T gear, you would be at 130.8 with a 42T rear in 3rd and 123.1 in 3rd with a 16/42 gear. With your trap speeds you should try a 42T rear sprocket first to see how it works. They are relatively cheap and easy to install and the stock chain works great. I hit a personal best tonight and, I am still learning, but the bike is much easier to launch than it was with the 16/42. 16/42 felt like insane gearing and the engine was buzzing on the freeway. The 41T rear gear is a 2.5% change and easy to do. The 42T rear gear is a 5% gear change and easy to do. Of course, if you are lowering your bike and strapping it and putting an extended swing arm on it, disregard all I have said. My bike is stock and set up for corner carving with 37PSI front and rear, even at the strip.