Never done the Fractions this low, so I can't comment on that. But I've done Brown's a number of times at this level. Not too difficult (though pretty challenging for rafts this low) but it becomes much more technical, though less pushy, than higher water. Pinball becomes a wicked S-turn under 650 and Raftripper/Widowmaker is pretty bony. Lots of fun. Enjoy!
"The world would be a better place if everyone kayaked."-Brad Ludden (Valhalla)
"You only get one chance to run a drop blind."-DD