I've seen a few fuel tank baffle or fuel slosh issue threads recently and I figured I would share something that I recently seen as a fix. The rock bounce/crawler guys have been doing this apparently for a while and it seems to work. There are even commercially available products that simulate the effects.
Those are Wiffle balls in there. They are fuel resistant (USA made name brand ones)
There are also commercially baffle rings that do the same thing.
http://www.alltechmotorsports.com/accessories.html
Thought this may be a solution for lack of fuel tanks with the built in baffle.