Double-wicking can be like using a blowtorch instead of a carmelizing chef's torch. Both will do the job, the blowtorch would certainly be faster but it's not necessarily better. If the ECO 8 was too small, then try a 10, then try a 12. I am not being flip -- some parts of this testing process are a little tedious. You also have to test all the way to the end/bottom of the candle -- melt pools behave different from the beginning to tne end. I have overwicked many, many times because I wasn't happy with my second or third burn and then ended up with a MP that was way too deep later on. Being methodical about your testing will get you the results you want, unless you want to rely on dumb luck which is what happens when you just skip around. ETA: doule wicking when it's not really needed can also lead to a candle being consumed faster than it was properly (single) wicked. And I can get a decent throw from a 7.5oz container with a ~3 in diameter -- it's possible without sticking more wicks in it.