The extra-large tanks like the Acerbis 6-gal do provide an excellent amount of radiator protection from sideways tip-overs. I never have noticed the sloshing of the fuel with half-empty tanks, and you don't HAVE to fill them up all the way for those shorter sections....But you WILL notice the difference in suspension when the tank is full.
"I don't know what you do, but I know what I do, and I don't do that." --Uncle Doug, R.I.P.
"Without the possibility of death, adventure is not possible"--Reinhold Messner