IMHO I think that it all depends on driving style, track type, Engine, suspension set up and tires. For bashing I guess its all up to you and where you go.
You want to make the center the highest from my experience. If you don't and you fill the front diff with the thickest you will experience push in the turns or the font end will "skip" across the dirt. The reason is the center diff gets all the direct power and is unloading it's power faster than the front diff can keep up because it has thicker oil in it. Always have the center unload slower than the front ie fill the front with 5k center with 7k and rear from 1-3k to start.