Heres what I run in my rears.
I run in salt, so I wanted to have room for some plastic tubs onto of the bags to catch all the salt water from my vests etc.
For full ballast, I run the Sumo 600's in the rear, a Sumo 900 in the cabin, Sumo 950 PNP bag under bow, and another Sumo 600 in the bow, plus the factory ballast. With all that along with some people, Im pushing a little over 5000lbs. I do have the high altitude prop and can plan out pretty quick at 5-10 seconds.
I was fortunate to get the upgraded pumps and 1 1/8" hosing in my 12' so fill times are pretty quick too.
When surfing, Im okay with just filling the surf side rear and adding the extra 600 onto of the tranny cover.