One thing to keep in mind when it comes to t/hulls, whether they be on a GW or any other builders boat. Virtually all t/hull hoses have to be hooked up after the boat is decked, therefore the rigger needs access to the t/hulls-drains to do this. Oft times this access is disguised in the form of a fridge, a tackle center, a rod pocket, an access pie, you name it.
So don't be afraid to pull some components/pieces and look behind them! I remember the first Proline 2950 I worked on in my side work (where I get paid WELL!). The fresh water tank, pump, and water heater were in an area behind the fridge, as well as the sink drain, water fill, and water tank vent fittings. Not where I would have put them, but, if you think about, remove 4 screws, pull the fridge out and set it on the cabin sole, and there everything is!
So just keep that in mind when trying to find sh!t...