Increasing the caster split helps the car turn into the corner easier and tightens it up on exit.  

RF CASTER:  Increasing this will help tighten the car on exit.  It saves a car that comes around to fast. The more RF you add the more the RF raises up when the wheel is crossed up.   I would stay under 10 and over 5.

LF CASTER:  Increasing this will help the car turn in.  The more you put on the left, the more the LF raises when the wheel is turned to the left.  This takes wedge out of the car.

CASTER SPLIT:  You can add more split which will turn the car in better and add bite on exit.  Staying on the high side (4-5 degree) will help keep the car under you when the tracks dry out.  If you go too far the car will feel uncomfortable and beat the crap out of you when the track is rutty.  I would run between 3-5 on the split.

I run 8RF 6LF on hooked up tracks and 9RF 5LF on dry tracks.  Some guys run 5RF and 1LF so you have to run what feels good to you.

CASTER CHANGES AT THE TRACK: I would avoid changing caster at the track as it screws with the toe out.  If the car doesnt have enough toe in it the caster doesnt come into play as much because the RF doesnt get turned to right far enough to raise the car up.  This also happens when turns are put in the front of a car. Sometimes people dont realize when they put a bunch of turns into their RF they have taken the toe out which actually removes the caster from the car.  to make a long story short, try to tighten the car up from the rear so you keep all your caster stagger in the car.