I'm pretty certain that if you wanted to do this(run two heat exchangers), that it would be best to run them in PARALLEL, not in SERIES. In parallel will get you much better flow. The Supercooler obviously flows better than the stock H/E, so why would you connect the lower flowing H/E in line with it? If I did this, I would neck up to larger diameter hose so that I could use a larger Y fitting at both inlet and outlet where you converge back to the stock diameter hose. The larger Y fitting would assist in keeping the best possible flow thru both of the H/E's.