Looks like you already flipped the steering rack on the 501x so that might be why you liked the steering from it
...
Anyways I tried the flipped rack this past weekend and it does make the car a bit more on edge for entry steering..
Now I have not run into the issue with the rear slapping on big jumps
... but I have switched over to a red rear spring and I like it a lot better
....
I will be putting the TRF503 on scales today to see how the weight is balanced out
and compare it to the TRF511 and TRF502x as well
Also patez... clean your car its dUrty