imo, i tried this set up during my 1st set up..... ur chiller will hit the set temp very fast, but ur main tank temp is still higher than the set temp...so very soon, ur chiller will start running again....not a gd idea cos u r feeding some water that juz exit from the chiller back to the chiller again. u can try feeding the chiller from the 2nd chamber of ur sump n output to the last.
else u can try using 2 return pumps. 1 direct back to main tank, 1 go to chiller, n back to main tank. alot of ppl r using this way n seriously i think this is still the best way.....