I just feed the tubing through the bottom of the sponge straight into the intake. At the bottom of the intake there was a fitting I guess for an air-line.
You said you built a spraybar the length of your aquarium? Wow! Now thats an idea. Currently I have two spay bars in my aquarium; one for the Ehiem and one for the powerhead. The powerhead spraybar is running up and down spaying along the back of the aquarium. Although I am having trouble with excessive current. Its like 400 GPH I wonder if I just build a spaybar the length of the aquarium that it would solve the current problem. Let me know how it turns out.