I have a 2004 Ski Supreme V220 Sky with factory ballast tanks in the rear of 350lbs each controlled by independent switches and Jabsco Ballast Puppy pumps.
I simply drew it out on paper, and then myself and my two year old daughter sat on the floor in the plumbing department of our local hardware store and started building it.
I now hav in addition to the stock ballast.... two additional 350lbs sacks in the rear and two 500lbs sacks in the bow underneath the seats. For a TOTAL of 2400lbs of plumbed in ballast.
I can also control which one is filled or emptied depending on which pump I turn on and which valves I open or close.
No problem switching from lots of people... to a few people.. or surfing regular or surfing goofy... a great addition.
The part I love the most is that I have everything just taking up storage areas I didn't use. And the stereo is totally concealed. with three 10" subs hidden throughout the boat. I still have all the storage in the cockpit area under the seats.
Have a great year riding everyone!