My thoughts are mixed....yes i ike them, but they are not as powerful as I had hoped- but thats my fault not theirs. Primarily it comes down to the back pressure on the pump. Im running a baracuda, which is not a pressure rated pump.
Before filling the tank with rock i tried the eductors on and without them. The flow was ost certainly faster with them on.
Your proposal is sound, but i would personally do a reducer to 3/4 then do loc line to the eductor. the reason is that you have to be able to "position" the flow, unless all you want to do is roll the tank barrel fashion.
Finally.....to get flow in a racetrack pattern you HAVE to concentrate the flow to be near the top of the tank. essentially friction with the sand will hamper the majority of flow across the bottom....but if you get the top moving, the bottom will follow suit.
Does that help at all G. ?
P.