How someone else did it may not be the right way to do it
That's even more true of boat builder installations than it is of owner installations, 'cuz boat builders' only concern is the least expensive way to do it.Basic guidelines: the tank should be within 6' of the toilet. Hose runs should be as short and straight as possible. Use a 1" vent, not the "standard" 5/8" size. Your best source for a tank is Ronco Plastics (no relation to the VegoMatic Ronco) http://www.ronco-plastics.com They make TOP quality plastic tanks for a very reasonable price and have more than 400 shapes and sizes, over 100 of which are non-rectangular. And they install fittings in the sizes and locations specified by the customer when they make the tank.You'll find lot more help at the link below...and I'm always glad to help you sort out the specific issues.