Nice build! 8)
I'm curious about what you're doing to get the chain to pass the wheel/tire and inside the frame. I know you brought the sprocket closer to the hub to gain some room. Are you using a 5/8" offset countershaft sprocket too?
I ran into similar issues with my KZ1000 build a few years ago. I ended up with a 5/8" offset countershaft sprocket and a 5.5" rear rim and a 180 tire instead of the 6" rim and 190 tire, to give us the chain clearance we needed.
Keep up the stellar work! 8)
Nice seat, BTW!