IMPACT- Who was running the body? If a newbie who finds it impossible to take the straighaway without turning in the middle is running a yok body, while josh cyrul is running and ascari, of course the ascari will look hooked up. Also you want to set your car up so it works with the body. The ascari (in lightweight trim, which ALL YOU EVER RUN FOR 12th, is actually very durable), however it has too much front grip for asphalt, so while it wont be undrivable, the car wont feel right, and could cause unwanted mistakes, since it will be hard to drive consistnatly.
On asphalt, you can NEVER have enough rear traction, and thats one thing that the yok body has. if you start to push, add front grip, dont take away rear grip. Also the yok body is rather durable (its more a of middle weight body with flexable lexan, no matter what they label it as).
I am not a pro-line driver, so I am just passing on what I have learned to help out.
carbon- A 10 double KR is alot of motor. All of the Reedy guys have actually been running the Ti in 12th scale (dont ask me why, but just an FYI). Also by the way you described it, it seems as if you are running 48 pitch gears. Pick up some 64 pitch ones. Try a 100 tooth spur, and pinions from 25-30. Also if you have no yet, run a stock motor first, it wont be as slow as you think, and it will be alot more driveable.