You're actually very close to what the factory sent us all out the door with, so breathe! There were 2 collapsible water bags, each connected to plastic tubing inside the sliding galley, one connected to fresh and one to gray. The spouts on the plastic water bags were attached using ss hose clamps.
I was unable to figure out how to get the full water bag in and connected without belching a good bit of it's load, and get the full gray water bag out without the same problem.
You'll find some of our colleagues have accomplished a variety of very creative ways to change the situation. For example, several have chosen to install tanks underneath running the tubes through the bottom of the galley and making a permanent installation of the slider, or getting rid of the slider completely and building in a usable permanent galley. There are others, but I wasn't willing to give up the flexibility of being able to remove the while unit if necessary. My solution to this "challenge" has evolved into the following. Since I found the sink to be too small to wash dishes anyway or do even a decent hand wash, I abandoned the use of the sink except for storage of stuff I need to access quickly. Plus if I were sailing more than a day trip, I found I needed lots of drinking water, especially on some of those hot humid Chesapeake Bay days. So when I'm out cruising for a week, I carry water on deck attached to the stanchions. Dishwashing is done in a plastic dishpan out in the cockpit using ecologically safe dish soap. And hand washing is done using waterless hand cleaner. I do use the galley for all kitchen storage (all plates, silver, cooking utinsels, pots and pans, etc). And I do find the flat surface to be perfect for cooking on my butane stove.
So, the builders didn't think this issue through, but they did build us a really great, fun boat, and I'm happy to work around this issue. IMHO. Good luck with whatever you decide!