So I got a 2010 lsv and wanted to install an IBS. I wanted 4 pumps but thought it was an expensive upgrade to put in a 4th pump for a 370 pound center sac... Between all the drilling, electrical and switch install work it was something I didnt want to get into... So I ended up buying the mastercraft 2 port manifold and installed it under the observer seat(pic below). which is easy to reach from the drivers seat.. I routed the 3rd pump line to the manifold then one line to the center sac and the other to the IBS. THe center sac and the IBS are about 1000 pounds so I can still fill them both quicker than the rear 1100 bag. I originally had just installed Y's but then I could only fill or empty them both. I wanted independent control of each sac so I could dial in the wake. The mastercraft manifold is 100 and is made from a solid block of aluminum. Wakemakers also sells a plastic version which is much cheaper...

If you like the idea of having control of all your sacs independently but dont want to drop a lot of coin and alot of your time installing a 4th pump this is another route for you to go...

By the way this for a GIII system with reversible pumps

When the lever is pushed forward it fills the bow, backward it fills the center sac