I have run my KF since they first came out and have loved every minute of it, probably the best car I've ever driven!
The car does drive better with the low grip chassis when the grip/weather is changeable. Out of the box the car is great on dry astro but would suffer when it's wet, running a ball diff, rear shocks on the rear of the arms and basic set up can make the car better in the wet but still it's better with the low grip chassis.
I suspect that Schuey will come out with a new kit in the not to distant future that will have the low grip or alloy chassis as standard so the car can run with saddles or a shorty out of the box.