I have the 6.6 gal tank, too, and it's really not that big when you get it on the bike. One thing that helps is that it's thin between your legs when standing, so it feels pretty normal.
I noticed in the picture that your chain looks extremely tight. You need to run it quite loose on these bikes or you will run into countershaft problems. Many guys take the shock out and adjust the chain by running the rear wheel through all it's travel to make sure you don't have a tight spot.