I have tried the lsd's front and rear and if the track is dusty at all the thing is a real handfull. Tons of steering but inconsistant, would be ok for a qualifier but I would never run it in a main.
Running a lsd in the front and regulare center and rear is fine with a wide open track but for me that setup pushed to much form me. I have run 3k in front and 7k center and lsd (black oil) in the rear and that is really pretty decent but for the most part I now run 3k7k1k and mess with the front castor and rear toe to get it fine tuned to track conditions.