I know I'm over thinking this but at least half of my tank dumps are at Flying J's where with my old rig, I would line up the drain pipe in front of the axles with the sewer, dump, and rinse. I'd then pull up, line up the drain pipe behind the axles with the sewer, dump, and rinse and be off.
With three axles now, the two drain pipes are about 8 to 10 feet apart. With only one split rinse, I can't see an easier way then to line up the center axle with the sewer, then rig a Y pipe(like Chuckster57 said) and two 4 foot sewer hoses(at least) to the Y and another 4 foot from the Y to the sewer. This would let me open both valves together and rinse together.
So, am I over thinking this? Is there a better way to accomplish the Flying J tank dump "dance"(given my setup)?