. so there are a cupple of problems with this design (this was the 4th design i tried out of 7 befor finding a good design. so the problem is that for the water to flow back into the sump the output line needs to be gigantic(around 1 inch pipe) or the skimmer has to be high above the sump. (from trial i found that the base of the skimmer has to be at the top of the tank) what will happen if you use this method is that water wont flow back to the tank fast enough and it will come shooting out the top. so to make it work i would eather use a slow moving pump(slow water movement is good for skimmers anyways), make shure the return pipe is as large as posible, and defenatly raise the skimmer (at least a cupple of inches)
oh. i just noticed something else. i would switch the output and the input so that the input goes to the bottom and the output comes from the top. this is very important. im having a hard time explaining why but for it to work like this the water needs to spill out the top as an overflow. i know that it wont be counter current that way, but the output has to come out the top.
the only reall way to know is to make it and see.
sory for the long post and good luck